Add unittests for check_code and load_codes
Add unit tests for door_loop

This requires restructuring door_loop a bit, so that we can run finite iterations of it.  I tried to
modify as little as possible though.
Add docs about how to run unit tests to README
Merge remote-tracking branch 'upstream/master' into add_unit_tests

Conflicts:
	baron.py
Merge pull request #4 from scottyallen/add_unit_tests

Add unit tests from scottyallen