* Small refactoring in Label._drawBackground()
* Added size calculation to Label, basic framework for detecting click on label.
* First fully working version of label click.
* Put in extra checks, refactored visibility of labels for more general usage.
* Final fixes to code; added to example and in docs
* Adressed review comments
* Add next attempt to fix Travis unit test bug
* Addressed review issues
* generate individual css files; fixes#1969
* simplified css bundleing
* add new generated dist-css files
* use chart specific css files in the examples