animatable object now notifies of animation event through the python.event module.  Related to issue #12
place the drawing related members into this class instead of the animatable object class
added CollisionMasks objects that contains bitmask for performing selective collision detection
started adding the methods for treating all game objects more generally
replaced action PLATFORM_LOST for PLATFORM_SUPPORT_LOST and PLAYER_IN_RANGE for GAME_OBJECT_IN_RANGE
moved collision support members to the GameObject base class
Level processes all objects (player and  enemies, thus far) through the same set of rules (issue #13).  Bitmasks are now used to perform selective collision detection (issue #14)