Okay so collision now works pretty well.
Most changes are in cells.py with the collidesWith(self, foe) function.
Based off of the electrostatics idea first put forward by Aaron, voted on
by everyone else, and coded completely by me (Brad Baker).
Peter Gui and Johnathan helped put forward ideas for collision,
which were not implemented.
TODO: Remove rounding which was done for safety, but may not be necessary.