Add ability to stop force animation

I've modified the webGLRenderer.html example to load my medium-sized graph data. It has 6,026 nodes with 5,885 edges. The webgl graph does a decent job rendering, however once the nodes have settled and it zooms out, some of the nodes are still animating (jiggling). Is there a way to stop this? I can make a video of the effect if need be...

Start with the webGLRenderer.html example and trace how the force animation behaves after the graph settles and zooms out. Determine how stopping residual node motion should be exposed, then verify the medium-sized graph no longer leaves nodes jiggling once settling is complete.

Written by the indexing model from the issue text.