Removed the special hack for 'Refinery Translator' role.

This adds complication to the core for a feature that could easily
be added by an extension when required.
Merge pull request #2730 from refinery/remove-translator-role

Removed the special hack for 'Refinery Translator' role.
Fixed bug: clicking Preview button causes Save button to open in a new browser window when clicked.
Implemented support for turbolinks, when it's present.

To enable it, just place it in the Gemfile of your application.