Add chipmunk dep
Chipmunk integration start. Doesn't work even close to correctly, but at least it's a start.
Make objects fall to the right direction
Add chipmunk dep to readme
Elasticity tests, clean up functions, etc.
Add local variable to scene object for specific scenes
Move chipmunk space handling to arena.c, and move har ticks and renders there too.
Merge pull request #13 from omf2097/new-physics

New physics