Attorney Docket No. 13-10035 ELECTRONIC HOOKAH BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an electronic hookah that may be carried around. Description of the Related Art In recent years, it has become popular among some to smoke through a hookah, also known as a water pipe. Hookah is believed to have been invented in or around the 1500s. A hookah is a large, free-standing apparatus that uses air pressure from a smoker sucking on a mouthpiece at the end of a long flexible use (see Figs. 1 to 3) to have air push smoke (from burning tobacco located in an upper portion of the apparatus) through water (in a vase portion of the apparatus) to filter and cool the smoke and then the smoke passes to the smoker's mouth through the hose and mouthpiece. The hookah is also known as a "hubble-bubble." The smoke is released at the bottom of the water and bubbles up to the surface, where it then may pass into the hose. A hookah generally has a bowl 2, which contains hot coal to heat air that passes into the bowl. A windscreen may be placed over the bowl 2. Tobacco is placed in a bottom portion of the bowl 2. A plate 4 is under the bowl to receive any falling ash from the coals 3. A body tube or conduit 5, normally rigid, may be connected to the plate at an upper end and communicate with a passage through the bowl. At the body tube's lower end, there is a water jar 6 into which the body tube extends and is immersed into the water in the jar. There is an air inlet valve 7 that communicates with air in the water jar above the water line. There is also an outlet 8 from the jar to a long hose 9 leading to a mouthpiece 10 on which the smoker sucks. Upon a smoker inhaling through the mouthpiece 10 and thus the hose 9, air is pulled down through the charcoal 3, where the air is heated, and then the heated air is pulled into the lower portion of the bowl 2 holding the tobacco. The hot air vaporizes the tobacco, thereby producing smoke. The smoke is goes down through the body tube 5 into the water. Then, the smoke bubbles up through the water, which receives heat from the smoke and helps filter the 2 Attorney Docket No. 13-10035 smoke. The smoke then fills the top part of the water jar 6. The smoker's inhaling on the mouthpiece 10 will make the smoke pass through the tube 9 and into the smoker's mouth. There is a reduction in air pressure in the jar when this happens, thus pulling more air through the charcoal, continuing the process. Hookah is typically used with flavored tobacco. An electronic cigarette, also known as an e-cigarette, personal vaporizer or PV, is an electronic inhaler that vaporizes a liquid solution into an aerosol mist, simulating the act of tobacco smoking. The electronic cigarette was invented back in the 1960s. It is disclosed in U.S. Patent No. 3,200,819 to Gilbert. An electronic cigarette has three things: A plastic cartridge that serves as a mouthpiece and a reservoir for liquid, an "atomizer" that vaporizes the liquid, and a battery to power the atomizer. Although electronic cigarettes have existed for about 50 years, and hookahs for longer, no one has thought to create an electronic portable hookah. Hookahs are large, water-filled devices while electronic cigarettes are small portable devices. SUMMARY OF THE INVENTION In accordance with one embodiment, there is an electronic hookah that is or may be made small enough to carry around. 3 Attorney Docket No. 13-10035 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a typical hookah device; Fig. 2 is a side view of another typical hookah device; Fig. 3 is a side view of a further typical hookah device; Fig. 4 is a schematic side partially cut away view of an electronic cigarette; Fig. 5 is an exploded view and an exterior view of another electronic cigarette; Fig. 6 is a perspective view of a mouthpiece for a hookah device; Fig. 7 is a side view of an electronic hookah in accordance with an embodiment of the invention; and Fig. 8 is a schematic view of the electronic hookah of Fig. 7. DESCRIPTION OF THE PREFERRED EMBODIMENT(S) In one embodiment shown in Figures 7 and 8, there is an electronic hookah which is or may be small enough to carry around and it includes: a mouthpiece 40 connected to a housing; a heater 44 stored in the housing; a battery 48 stored in the housing for operating the heater 44; a cartridge mechanism 50 for containing a substance vaporizable by the heater 44 and to be smoked, the mouthpiece 40 communicating with the cartridge mechanism 50 for receiving the vaporized substance in response to a smoker inhaling through the mouthpiece, like a big electronic cigarette; and where the housing is preferably in a form of a tube section 52 of sufficient size to be held in a palm of an adult and having a cross section of a typical hookah tube, where the mouthpiece 40 and hookah tube 52 are separable for inserting and removing the cartridge mechanism 50, and where the mouthpiece 40 is sized and shaped as a typical hookah mouthpiece. 4 Attorney Docket No. 13-10035 As shown in Fig. 7, there is an electronic hookah that is or may be made small enough to carry around. There is a mouthpiece 40, a coupling 41, a body/hose 52 and an end cap 53. The look on the exterior is the same or similar to a standard hookah. The look itself is not functional. What is important is the size which is the same or comparable to a typical hookah mouthpiece and section of the hose proximate the mouthpiece. The mouthpiece 40 may be integral or unitary with the coupling 51. The coupling 51 may thread or snap onto the body/tube 52 or otherwise connect to the body/tube 52. The coupling 51 could be its own piece as well, with the mouthpiece 40 connecting to it and the body/tube 52 connecting to it, or the coupling 51 could be unitary with the body/tube 52 or otherwise attached. The end cap 53 may be threaded or otherwise attached or unitary with the body/tube 52. As shown in Fig. 8, inner structure of the electronic hookah may resemble that of an electronic cigarette but preferably with greater capacity/size. An LED mechanism 55 which is typical in an electronic cigarette to simulate a burning cigarette in look may not be needed. However, the LED mechanism 55 may still be included as it is also a useful way to indicate proper operation of the device and low battery or other issues. The mouthpiece 40 may house a removable cartridge mechanism 50, e.g., a single cartridge or multiple cartridges. The inner structure's cartridge mechanism 50 may be located in the mouthpiece 40. Alternatively, given that the device is preferable significantly longer than a cigarette, the cartridge mechanism 50 could be housed in the body/tube 52. The cartridge mechanism 50 contains liquid for producing vapor such as in electronic cigarettes. The liquid is known as e-juice or e-liquid and is typically a solution of propylene glycol (PG) and/or vegetable glycerin (VG) and/or polyethylene glycol 400 (PEG400), often mixed with flavors. Optionally, a variable percent of a liquid nicotine concentrate may be used. 5 Attorney Docket No. 13-10035 The cartridge(s) are often sold in a bottle or as pre-filled disposable cartridges. Various flavors which resemble the taste of regular tobacco smoke (from a hookah), menthol, vanilla, coffee, cola and various fruits may be provided, and this may include mixtures of flavors as is typically done in hookah smoking. Nicotine concentration may vary from zero to larger amounts as desired. Nicotine-free solutions may be most desirable. Some electronic cigarette users opt to make their own e-juice in a form known as "DIY" (for "do it yourself") and that same concept may be used for the electronic portable hookah. There is also an atomizing device typically containing a heating coil 44 (like in an electronic cigarette) in liquid communication with an inserted cartridge. Suitable mechanisms for such communication would be evident to those of ordinary skill in the art, and may include, e.g., a metal mesh dome 45 or wick to bring controlled amounts of liquid to the heating coil. Upon inhaling on the open/free end of the mouthpiece 40, a pressure sensor/voltage controller 58 (PS/VC) senses the change in pressure and in response thereto electrically connects the battery to the heating coil via electrical connectors and wires 59, as in electronic cigarettes. The battery 60 may be rechargeable or single use. The air pressure change (lower air pressure in the body/tube 52 and mouthpiece 40 in response to a smoker/user inhaling) may directly, or also through the PS/VC connection being enabled, cause liquid from the cartridge 50 to leave an opening in the cartridge, wick to the heating coil 44, and be vaporized, whereupon the vapor escapes through the mouthpiece 40 in a passage or passages/opening between the cartridge and the rest of the mouthpiece (or body/tube 52 if the cartridge 50 is in the body/tube). The heating coil 44 and cartridge mechanism 50 may be made in one piece, as is sometimes the case for electronic cigarettes, which is called a cartomizer. There could also be, in 6 Attorney Docket No. 13-10035 lieu of the PS/VC 58, a button on the outside of the electronic hookah that causes atomization. The user presses the button, ideally when the user is inhaling or about to inhale. To simulate the fact that the smoke is cool in a hookah, the vapor should already be sufficiently cool. For simulating a hookah, the dimensions of the electronic hookah would preferably be comparable in diameter to a hookah hose and a hookah mouthpiece, and the dimensions of the mouthpiece length would be the same or similar to a hookah mouthpiece. The length of the body/tube (housing) would preferably be at least as long as the width of most human hands (so that it may be grasped like a hookah) and although it could be fairly long, preferably the entire length (mouthpiece 40 and body/tube 52) would be no more than twelve to eighteen inches long. Since a human hand is typically around 3.1 to 3.3 inches wide, preferably the length of the body/tube would be at least three inches. Preferably, the length of the body/tube 52 would be in a range of two and a half inches to eighteen inches and more preferably three inches to twelve inches; Preferably, the length of the mouthpiece would be in a range of one inch to eight inches and more preferably two to six inches; Preferably, the length of the mouthpiece and body/tube together would be in a range of three and a half inches to twenty six inches and more preferably five to eighteen inches; Preferably, the diameter of the body/tube and the diameter of the mouthpiece would be in a range or ranges as set forth in the below and in the claims. In other embodiments, the housing is at least one inch in diameter, at least one and one half inch in diameter, at least two inches in diameter, at least two and one half inches in 7 Attorney Docket No. 13-10035 diameter or at least three inches in diameter and a maximum of at least three inches in diameter, four, five or six inches in diameter. Although the invention has been described using specific terms, devices, and/or methods, such description is for illustrative purposes of the preferred embodiment(s) only. Changes may be made to the preferred embodiment(s) by those of ordinary skill in the art without departing from the scope of the present invention, which is set forth in the following claims. In addition, it should be understood that aspects of the preferred embodiment(s) generally may be interchanged in whole or in part. 8