Adding hidableStacks as an option for stackableChart to hide/show stacks.
Greying out legend labels on hiding stacks.
Fixing bug around color of stack dots not being the same as color of the chart when other stacks are hidden
Removed extraneous spaces in title documentation
Fixed bug where BarChart stacks did not have individual titles
Documented hidableStacks
Hovering over hidden legend items should not fade out other stacks