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) 
Why is there a _Discussion_ and a _DiscussionItem_? From what I see the _DiscussionItem_ is not inside the _Discussion_ and I believe the naming is confusing.

Also, there is a _Page_, which is a "second level" layout, and I believe it's on the same level of the _Discussion_. The naming should follow a pattern.