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 example can be reduced to `$ python -m unittest discover` since unittest has auto-discovery.

I don't think example 3 and 4 are necessary, should be safe to remove. You can summarize the info they add in example 2 by adding a tip about the `-v` and `-f` flags.