Use Oj gem to escape JSON as ascii

Submitting as a potential fix for jsonp requests that contain embedded UTF.

Blog post that describes the issue: http://omegadelta.net/2013/04/28/changes-to-how-rails-3-2-13-and-4-0-encodes-unicode-in-json/

It recommends using: ``JSON.generate(object, :ascii_only => true)`` but that doesn't appear to work.

Difference between JSONP requests between Rails2 & 4 when the document's description contains UTF.
https://gist.github.com/nathanstitt/4c790f6d984180a53c29