* Changed CSS for GradeBook buttons to match wp-core-ui. 
* Fixed a bug where cells multiple copies of rows and columns were being displayed.
* Changed CSS for chart view on students gradebook to match that of the admin view.

git-svn-id: https://plugins.svn.wordpress.org/an-gradebook/trunk@882720 b8457f37-d9ea-0310-8a92-e5e31aec5664