Adding tests & other minor tweaks

Major changes:
- Moved `__init__.py` code to `wex.py` and removed `load_wex` and `wex_files` methods.
- New `__init__.py` that keeps the API functional, but is a bit cleaner and exposes the `base.py` classes
- Added some quick rough unit tests, mostly `assertEquals` at the minute.

Minor changes:
- Tweaks to conform to pep8
- Removed some unused variables

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On the subjects of tests, `GameRules.active_pick` throws a `KeyError` with the test.dem provided, whereas `GameRules.first_pick` returns `Enum("NOT_CM", 0)`; I'd have expected `active_pick` to also return that Enum so I set up the tests to expect that Enum, and thus interpret the current behaviour as an error.