Adds circle support to spread
Merge branch 'master' into feature/ar_recipies
WIP: NoUpdate return message
First working draft of skipped server update when render parameters are unchanged
make toolbar visibility toggleable
Balance zoom only used in initial calculation.  Fixes #1114
Resiliant to lack of render state
Recipies for hdalpha and heatmap.
Used the Bar chart as a starting point for heatmap.
Completed a simple HeatMap implementation. Also added examples.
Made the color mapper more generic.
Now supporting palettes.
Avoid grids in some categorical charts.
Removed checkpoint folder.
Change names and fixed examples.
Reworked many examples for recipies
Everything but ISO Contours seems happy.
Added HoverTool.
Merge master-in, fixed conflicts.
Updated tests