initial addition of physics
actually update entities based on physics results
Improve physics system, and write some wrapper in Entity
fix some potential issues with sprites/entities
Change TiledLayer implementation to use actual tile entities
remove dead code
Add collision handling for tiles
move position stuff to DisplayObject from Sprite
move position stuff to DisplayObject from Sprite
optimize the creation of the tile entities a bit
all DisplayObjects now have a game instance (except GUI)
convert to Chipmunk for physics, and fix some bugs
oops
typo
maintain collision state
update readme with physics info
re arrage goals
Merge branch 'physics'
also try to use char codes
also try to use char codes, with delim