Make depay to chant magics

- Magic.is_chanting is added.
- Magics need exist in Rein.objects while it haven't made effect.
- If magics exist in Rein.objects after begining of working, ther need
  set False to Magic.is_chanting.
Delete TODO file because it isn't used any longer
Remove a needless import
Implement MP system

- Entity has MP in self.userData['mp']. I'll let b2Body and b2Fixture
  have MP.
- Monitor shows MP.
Fix a mismatch between types
Add Entity.userData['name']

- The format in 'class_name'.
- Entity.__init__ automatically set it from self.__class__.
- Modify format of b2Body.userData['name'] to 'body_name' from
  'class_name.body_name'.
- Add b2Body.userData['owner'] to get 'class_name'.
- b2Body.userData['owner'] is set at Entity.append_body.
Improve rein.game much

- Rename rein.game.Game rein.game.GameObject.
- The __init__ takes game var (Rein).
- The update increments age attribute.
Improve Magic

- Modify Magic.__init__. The arguments are self, game, cost, delay and
  user now.
- Magic.on_chanted callback is added.
Override GameObject.leave_game at Entity

- Entity.leave_game destroys the bodies.
Rename pygame_event to on_pygame_event