Merge branch 'upstream'
Merge branch 'master' into develop
Fix for bubble series selection

Adds the groupKeyFunction to allow cross filtering with bubble series.
Add tests

Tests that the correct key is used for the class name of an item, used
to do selection of bubbles/columns.

Also removed the rootClassName, as this was used to set the itemClassName
but only once drawing had been done.
Bump to 1.0.1

Updates the change log, read me and bumps the version number
Update README.md

Includes notes on 1.0.1
Merge pull request #116 from tpkelly/develop

Introduce groupKeyFunction