Signed in elements

After chats with @stephanfowler and @phamann, I am going to be looking at making signed in elements visible / hidden dependant on classes.

This was the best situation between:
* Doing the logic on the server rendering on the same URL and breaking the cache. **Problem?** Breaks cache
* Having a separate URL for signed in content. **Problem?** Weird, and if calls aren't through XHR, creates template logic that breaks the cache.
* Creating content in the JS. **Problem?** It's getting very very messy already.

** What next? **
We'll be applying this logic to the reply buttons on discussion.

P.S. In the name of tiny Pull requests, this one is tiny.
![Rockin!](http://www.furrytalk.com/wp-content/uploads/2010/11/11.gif)