Fix migration script for Masterfile.display_aspect_ratio

If there is no workflow to reference to find the display_aspect ratio, Mediainfo is ranon the absolute_location of a derivative instead.
If that fails, the user is warned that setting the display_aspect_ratio failed for that pid.
Set display_aspect_ratio to default of 4:3 if ratio can't be found.
Merge pull request #253 from avalonmediasystem/bugfix/VOV-2431

Redirect to return url with error message when lti oauth fails
Merge pull request #252 from avalonmediasystem/feature/VOV-2448

Fix migration script for Masterfile.display_aspect_ratio
Bump version of rails to 3.2.17 to get fix for DOS that targets render :text
Merge pull request #259 from avalonmediasystem/bugfix/render-text-DOS

Bump version of rails to 3.2.17 to get fix for DOS that targets render :text
move dropbox documentation link
Merge pull request #260 from atomical/task/move-dropbox-documentation-link

move dropbox documentation link
Change error message based upon feedback