Famous/famous — pull request #526 by timjchin (2014-12-15 22:13:13+00:00)
Title: Collisions: Incident velocity & lambda cleanup

This PR does two things:
1. Removes a gamma variable which was always 0.
2. Prevent's the collision from applying the impulse if the spheres are moving apart from one another.

@AdamCmiel was a huge help with this, thank you.
@michaelobriena