* Removed jquery post/get calls and replaced them with backbone fetch,destroy,save. 
* Added pointer to .course and .student cells to indicate selectable cells.
* Added default cursor to all other td cells.
* Bug fix: When adding an assignment to a new course, the assignment gets created but does not render.
* Added sorting in both directions: dec and asc.
* General performance enhancements (reduce function calls and http requests).

git-svn-id: https://plugins.svn.wordpress.org/an-gradebook/trunk@1028278 b8457f37-d9ea-0310-8a92-e5e31aec5664