The starting velocities going outwards in a circle means that the sum of
energy in the system is 0. As the boids come back together, they will
slow down to fall into a lattice. This is interesting, but not the
flocking behavior Boids are supposed to have.
I've replaced the `space_brakes` function with this new speed controller
to keep boids moving between two speeds. Anything too slow will speed up
along it's current vector, and anything too fast will slow down.
Robert Garrett
dca8bcdaa7