Partially Implemented Sort Functionality - Needs Work.
Finished Item Sorting Implementation.

- Finished initial implementation of sorting directive that wraps jQuery UI sortable.
- Added sort action in Rails
- Still need to add unit and e2e tests for both Rails and Angular
Continued Item Sorting Implementation.

- Moved the item sort action in Rails to the Items Controller (which is where it should be).
- Added a Rails unit test for sorting, still need Angular unit and e2e tests.