Dev/jpsnyder/debug/led

- Cleaned up sprite implementation and fixed some bugs.
- Implemented line function in C instead of python.
- added a "tests" folder and the ability to run these tests by calling "setup.py test" in the terminal

In general, I'd prefer the code to be in Python UNLESS there is a performance improvement in C.  The simple test would be to run this function a million times for a long diagonal line, and compare the time.

This is complicated a little bit by the fact that the new ALGORITHM certainly does look faster (it has no multiplies per loop, whereas the old one had 2).  So, to do a Python to C compare, you have to compare the same algorithm.

Let me know what the time difference you see - if its negligible (or (unexpectedly) worse), lets stick with Python.