Gallery's charts generator.

git-svn-id: https://plugins.svn.wordpress.org/nvd3-visualisations/trunk@903760 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme update.

git-svn-id: https://plugins.svn.wordpress.org/nvd3-visualisations/trunk@903763 b8457f37-d9ea-0310-8a92-e5e31aec5664