Optimization to CCNode & basic positioning
Optimizes CCLayout, fixes #370
Updating to the latest Chipmunk version.
Implementing CCPhysicsBody.affectedByGravity and adding more unit tests. Fixed a bug with CCPhysicsShape.group.
Updating the Chipmunk project reference.
Merge branch 'develop-v3' of github:cocos2d/cocos2d-iphone into develop-v3
Merge branch 'develop-v3' of https://github.com/cocos2d/cocos2d-iphone into develop-v3