Routing filter

This pull request is the result of the discussion between @jerboaa, @danielstjules, me and Alan and Sue from UofT.

The global behaviour of MarkUs concerning locale is unchanged. I removed a gem we used to do locale filtering. I'm now doing locale filtering with Rails 3 framework.

Once this patch will be integrated into master, I'll backport it into MarkUs 1.0.x branch and release MarkUs-1.0-rc1

poke @jerboaa @danielstjules @reidka