Zamboni physics update and EventHandling refactor

Zamboni EventHandling Refactor: There was a redundant MousePress check
in both PlayState and Zamboni class, the first handles motion, and the
second handles. Motion handling moved from PlayState class to Zamboni
class.

Motion Update: , Zamboni doesn't move at constant velocity anymore, and
accelerates. Zamboni also slides on ice.
Merge branch 'master' of https://github.com/danava04/ZealousZamboni