TDD

I suggest that, since we are starting with both a spec and and a reference implementation, we go the Test Driven Development route.

This raises the question, what test framework do we use? I'm most comfortable with unittest, but am entirely open to learning pytest or Nose.

Additionally, I was considering an essentially 3-branch structure: `release`, `master`, and `unimplemented`, where `unimplemented` holds tests for new features that have yet to be implemented. Upon those tests passing, `master` would receive both the tests and the code to pass them. That way, we can enforce an always-passing rule on `master` more easily.