Add a proper .gitignore to stop .pyc files from getting into the repo.

This is basic repository sanitation, so.
Removed global state, and fixed problem where all rounds were 10:0 or 0:10.

The old Arena.py always returned the same buffer object to RunThisTournament.py
causing all results to either end up as 10:0 and 0:10. Also, the global state
in Arena.py is /terrible/ now that it is a module and not a standalone program,
so, I killed that.