Fix categories and nodes relationship
Remove failing cucumber tests

These tests should be reimplemented as the CSC517 projects are completed.
Add the rails4 branch to travis
Add tests for the student_task model
Fix the schema file for Travis
Fix associating an assignment with a course from the assignment.
Clean up due_dates in assignment#edit
Clean up assignments#edit for due_dates
Add a missing jquery plugin. Fixes due_dates in Assignments#edit
Add indices to the response_maps models
Clean up participant/response/response_maps relationships.
Destroy participant response_maps when a team is destroyed. Closes #428
Add a route for POST users#list. Fixes #429

Add a test for this bug as well.
Fix impersonate#start form button
Replace missing images for assignment in tree_display#list
Fix remaining javascript errors in due_dates
Fix the late_policy system
Update impersonation form to the right of most pages
Add a helper to retrieve a participant's team
Fix hyperlink adding/deleting on submitted work. Fixes #426

This bug was caused by trying to display the team hyperlinks while updating the
single participant's hyperlinks.