Games for a multitouch table.

After installing dependencies (Kivy, Numpy, Cython), run
`python setup.py install`, then try the games:

maze.py: A two-player game where one player solves a maze while the other
    modifies it.
towers.py: Two-player tower defense -- hold out against an invasion for as long
    as possible.

For data collection purposes, all games are logged and can be replayed using
`replay.py <logfile>` (given replay.py is started with the same parameters,
e.g. screen size).