Adding CSS transform to particle views (significantly improved dragging performance)
Updating .gitignore to cover node.js modules and the build files
Temporarily remove the nucleonLayer from the scene while we rebuild the nucleus
Removing unnecessary mutate call in inner loop (the overall ParticleCountDisplay isn't pickable, so children of it don't need to be unpickable)
Optimization of the ParticleCountDisplay changes (only creating 1 new node at a time, reusing where possible, only executing one addChild at a time). Adding pass-through options to ParticleNode.
Instead of re-creating the meter arrow node every change, we just rotate it
Minimize changes to the numerical charge readout
ChargeComparisonDisplay optimizations for Scenery usage (less mutation, significantly less nodes created/destroyed/added/removed)
Removing missed console.log
Removing nodes first before adding in AtomTabView's rebuild nucleus, so we can minimize overhead
Minimizing dynamic Scenery changes in MassNumberDisplay
Lint fix
Merged in performance enhancements done by Jonathan Olson.  Also modified nucleus layering algorithm for better efficiency.