1. implemented customized animation 2. two API changes:      call self.obj.show() to show out the object      call self.obj.patches() to return the list of patches to be updated in      each frame (called in step()) 3. the runway: slightly flatter loop
1. implemented customized animation
2. two API changes:
     call self.obj.show() to show out the object
     call self.obj.patches() to return the list of patches to be updated in
     each frame (called in step())
3. the runway: slightly flatter loop

BrianOn99/roll