TODO

Impulse should do ZERO WORK when in a quiescent state.  (not even spinning
                                                             requestAnimationFrame
                                                             no-ops)

Rename `damping` to `restitution` for acclerate.

Throw error if using renderer and no styles are defined?

CSS animation generator.  Sometimes you want a spring or acceleration
animation, but you want it always starts with the same initial velocity and
position.  In this case it would be much smarter to generate a css keyframe
animation, and cache it.

Performance instrumenting.  Use something like,
http://google.github.io/tracing-framework/, to get better insights into where
the performance bottlenecks are.  The goal would be to be able to simulate
100's of springs without any performance hit.

Angular rotation.  Add a way to do angular rotation. (not the framework, like angles)

More examples.  The more examples the better.  If you have an idea for an
example you'd like to see created, create an issue.

Use analytical solution for acceleration and deceleration.  There's may be no need to run a physics simulation for acceleration and deceleration, since these are pretty easily computed analytically, which would be much faster than numeric integration.

Accumulator timestep with alpha smoothing.  Instead of just using whatever time the browser throws at us we should have a fixed timestep, integrate over those steps, and then linearly interpolate between states with unused time at each render, i.e. set timestep to Yms, update every Xms, and interpolate any extra time.