Fixed crash when all stackableChart stacks are hidden
fix to dots color on line chart
Fixing bug around title of LineChart stacks being incorrect when other stacks are hidden
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
some optimization for computeOrderedGroups
Merge pull request #382
only set dash attr if dash style is set
Merge pull request #385
Legend items show with dashed lines of the appropriate stroke-dasharray

This makes the most sense for a composite chart with several line charts that have different dash styles.

If any of the legend items have a stroke-dasharray property, all the legend items will show as lines.

Added an example with a composite chart that has different dash styles for each line graph.
Merge pull request #393
Use queue for composite example, lint