Collapsible Header

To take full advantage of height in the UI for code annotation, I would like to propose for the Header element to be collapsible and revelled on :hover on top area.  

![image](https://user-images.githubusercontent.com/1746146/36783888-76c96b6a-1c75-11e8-935c-d245c87a6534.png)