renamed animatable_object modele to game_object_module
renamed method animation_set_progress_percentage to get_animation_progress_percentage for improving clarity of the intent for this method
animatable_object now manages all animation using an internal animation_sprite object of pygame.sprite.Sprite type
no longer makes use of the collision_sprite member to perform collision queries.  All such collision queries now handled with the rect member
renamed some methods
calls the enter() method of the active state in the state submachine when it is entered/re-entered
added some enemies