Properly update Renderer.can_render

[VirxEC]

Fixes #37

[NicEastvillage]

I do not think this solution is ideal as it couples the renderer to the manager and will it not work correctly without it, thus reducing flexibility. For example, I cannot make a custom renderer and have its can_render flag update, unless I store it as self.renderer in my bot or override the msg handler.

I suggest putting the can_render flag on the RLBotInterface and then have the managers and the renderer read that flag instead.

E.g. in the renderer:

@property
def can_render():
    self._game_interface.can_render