stop the renderer from running when updates aren't coming in
Add a method to force rendering

You'll now need to do this if your style functions have side
effects that aren't part of the position of the object.
reset changed, and check if either of the directions change, not if both change ;-)
cleanup new acceleration syntax
acceleration fix
Merge branch 'accelerate-fix'
Merge branch 'fix-infinite-render'
changelog
CHANGELOG
Merge branch 'master' of github.com:luster-io/impulse