#424 Improved the stuttering effect for non-force layouts. They stutter if transitions are re-triggered when new nodes or edges are added. I made the easing linear, and account for time since the last transition so that the overall transition time is somewhat conserved, but so that new calls do not extend it. This is not the best implementation possible, but it works alright. It could be improved by passing the reason for the refresh (bad), or checking to see if a transition is already underway (just thought of it).