Add a scGroupedBar directive
Add scCombined directive
Chart directives check data chart type.

Before processing the data (e.g. to build scales)
chart directives checks they received the right
type.

TODO: validate series.
add test to round filter
add test for sidebar controller
Merge remote-tracking branch 'upstream/master'
Merge pull request #11 from dinoboff/master

All existing chart have tests