Corrected bug in drag reheating
Corrected bug in drag reheating

My previous method of reheating the simulation on drag events
(change alphaTarget) allowed some unintended interactions in the
y-positioning forces and collision forces (nodes moved far from
their initial y location created a vertically-offset collison
area).  New method of prescribing alpha and restarting, both on
drag start and end, seems to work much better and avoid this
artifact.

kakearney/d3-foodweb