UpdateManager()
I am planning on taking this class out in the next version of rabbyt. If you want it to stay, drop me an email explaining why and I might change my mind.
This is a small helper class for keeping track of physics drivers that need updated.
All physics drivers are stored as weakrefs, so you don't need to worry about removing them.
There is a global update manager at rabbyt.physics.default_update_manager. All physics drivers are automatically added to it.
update(dt)
Update the physics drivers by timestep dt.