Target: Use ChipmunkPivotJoint and ChipmunkRotaryLimitJoint to setup a grabber.

 1. setup ChipmunkSpace, MultiGrab, DebugLayer and Update as usual.
 2. setup every Chipmunk Body and Shape properly, add Grabber head and tail on it.
 3. setup ChipmunkPivotJoint and ChipmunkRotaryLimitJoint to setup a grabber's ability.