Discussion page style

- Change style of the discussion page
- Remove header bar from application
- Add individual headers to each page

![untitled](https://cloud.githubusercontent.com/assets/4236592/5455850/076350c0-8537-11e4-9804-dcdf0e143955.png) 
The _DiscussionItem_ is used inside a _Page_. That's the only thing that matters, I would expect _DiscussionItem_ to be used inside a _Discussion_.

My idea is that you should rename  _Discussion_ to something else, even  _DiscussionPage_ is way better. You'll probably have a lot more things like _Page_.

The style from _DiscussionItem_ is very similar to _Comment_ right?