Shamelessly leverage code from example.py as unit test

[carljparker]

We want to get some coverage on easy_music_generator.py and pregenerator.py, so I am leveraging the code that we use for our example (from example.py) as a test case.

Here are the results . . . but I feel a little as though this is not in keeping with the spirit of unit tests . . . That I am testing at too high level.

Name                                            Stmts   Miss  Cover
-------------------------------------------------------------------
easy_music_generator.py                            37      0   100%
pregenerator.py                                    29      0   100%
preprocessor/__init__.py                            2      0   100%
preprocessor/chord_distribution.py                 40      0   100%
preprocessor/note_distribution.py                  53      1    98%
preprocessor/preprocessor.py                       27      3    89%
preprocessor/tests/__init__.py                      0      0   100%
preprocessor/tests/test_chord_distribution.py      35      0   100%
preprocessor/tests/test_note_distribution.py       37      0   100%
tests/__init__.py                                   0      0   100%
tests/test_easy_music_generator.py                 18      0   100%
-------------------------------------------------------------------
TOTAL                                             278      4    99%