Add routes for repository tag editing.

This is to fix the following error:

Error caught: [ActionController::RoutingError] No route matches
{:action=>"tagging_edit",
 :id=>nil,
 :db=>Repository(...),
 :escape=>false,
 :controller=>"repository"}

http://bugzilla.redhat.com/show_bug.cgi?id=1138120
Add missing route and a spec fix

http://bugzilla.redhat.com/show_bug.cgi?id=1138120
Merge pull request #510 from mzazrivec/fix_repo_tag_routes

Add routes for repository tag editing.