Merge pull request #1 from desplesda/master

Add initial versions of cocos2d-chipmunk-nodes.
Move dragging logic into PhysicsObject
Add collision callbacks to physics objects
Add control for toggling physics debug view
Merge branch 'master' of https://github.com/thesecretlab/piecewise
Fix a lingering merge conflict
Better support for removing objects from the world
Fix a bunch of crashes related to objects being removed from the simulation
Fix a boneheaded math issue in grabbing and dragging
Remove some logging code
Fix an infinite recursion
Call a method for each object that's about to be updated with physics. Fix a collision handler error.
Fix some memory issues
Add childWithIdentifier:
Update collision logic
Don't crash if a child needs to be removed and its body is NULL
Add a property (designed to be overridden) that changes when a PhysicsObject starts dragging
Increase wall thickness
Allow objects to shut down their physical simulation
Merge pull request #2 from thesecretlab/master

Updated content.