added dependent destroy to submissions
added before destroy method to remove submissions
added letter grade method and moved total earned into if statement
changed way that grades are shown
changed from delete to destroy
changed way that grades are calculated and displayed
changed way that grades are calculated and displayed
changed way that grades are displayed
removed method of assigning current grade
changed way that percent is calculated on swot report
changed way that letter grade for student is calculated
changed way that grade is calculated
modified code to only display grade and percent if student submitted assignment
Merge pull request #202 from rwarbelow/assignment_delete

Assignment delete