Reorganization, Refactoring, Re-modularization, and other wonderful things

* Generalizes documentation and package name to reflect that this library is not limited to only the TekPower 4000ZC, and instead supports all FS9721-chipped DMMs.
* Repackages for distribution on PyPI.
* Refactors commandline handling to use PyPI entry points.
* Refactors measurement handling to use [python-measurement]
(https://github.com/coddingtonbear/python-measurement) measurement objects.
* Refactors module into multiple submodules.
* Cleans up code to match [PEP-8](http://legacy.python.org/dev/peps/pep-0008/) (excepting PEP-8's preference for snake case rather than camel case).

After merging -- assuming you'd like to -- I recommend that you take the following couple of actions:
* Change the repository name to `python-fs9721`.  Since this library supports many more multimeters than just the TekPower 4000ZC.
* Send me your e-mail letting me know what your PyPI username is, and I'll transfer the PyPI record to you :smile:.

Feel free to apply this patch manually if you'd like to not have my name on almost every single line; I'm not at all worried about attribution -- you did the hard part, I just did a little housekeeping for you.

Cheers!