Add UnEdditReddit module to RES

Adds a module with the same functionality as the bookmarklet at http://www.unedditreddit.com/, except instead of needing to activate a bookmarklet it is a link on all edited/deleted comments. Requires a new XHR permission for unedditreddit. I've added this to the Chrome manifest, but I don't know how to do it for other browsers so would appreciate some help there.