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.
Reworked many examples for recipies
Everything but ISO Contours seems happy.
Updated tests
Fixing isocontours and hdalpha recipies
Merge branch 'master' into feature/ar_recipies
Add Button widget and stubs for Toggle and button groups
updates to allow pip packages to install cleanly
some initial cleanup
add readme make consistent with other app examples
Merge of master
Corrections on examples
Added bivariate function dataset