Canvas optimization of ShakerParticlesNode, including passing in additional information into the node, and adding a catch-all change listener in ShakerParticles.
Adding a few pickable: false flags to speed up hit testing
Fixing accidental omission of sqrt(2) in size computation
Setting the ShakerNode to use CSS transforms for the SVG parts
Optimizing out a few immutable calls in inner loops
remove obsolete add/remove listeners
remove unused import
doc
merge 'performance' branch with JO's performance enhancements for shaker particles, #16