Redirect user back to root_url if they timeout and make Ajax request
Merge branch 'issue-577' into redirects

Conflicts:
	app/views/graders/index.html.erb
Updated PR-981 to display a modal when the user performs an ajax call and the session has expired
Merge pull request #1177 from danielstjules/redirects

Closes #577: Display modal on failed ajax calls from expired sessions