Submit/Save Functionality Working

Need to move logic from assignment/show view to assignment controller show method. Need to render completed essay title and content from assignment/_student_assignment_overview partial if essay has been submitted.
Submissions displayed in correct assignment view

Displayed in editor or as plaintext depending on completion status. Moving logic to controllers.
Fixed editor showing for complete essays bug + cleaned up code
Forgot an end in assignment controller
Merge pull request #48 from whoisglover/submit_save_functionality

DG reviewed, looks good.