Documentation update for issue #467

Added information that refrences setup.py's unit testing functionality.
I have updated the examples that refer to unittest. Should the be removed? Will a developer still find the unittest commands to be useful when they are trying to run a specific test?
This section should be removed as eventually we'll start writing tests in the [pytest way](http://pytest.org/latest/example/index.html). Python's `unittest` will not pick up any of these new style tests.