Move issue title to the top of the page [Awaiting developper feedback]

Every time I look at a GitLab issue I feel my eyes wondering for 2 seconds to find the title.

Titles should be one of the first things we see on pages.

After: remove "Issue" since already on the tab, put the title there:

![screenshot from 2014-11-16 18 51 02 after](https://cloud.githubusercontent.com/assets/1429315/5062429/263d7a8e-6dc2-11e4-82d6-90581e2f5763.png)

Before:

![screenshot from 2014-11-16 18 53 24 before](https://cloud.githubusercontent.com/assets/1429315/5062431/2be126fc-6dc2-11e4-88a5-5fdf2662203c.png)

It gets even worse if there are headers in the description, since even an `h2` is larger than the title:

![screenshot from 2014-11-16 18 54 08 before with header](https://cloud.githubusercontent.com/assets/1429315/5062438/3b64554a-6dc2-11e4-9275-d69bb1b8a49c.png)

This is also closer to how GitHub looks.

If you like this, it should also be done for merge requests and milestones simultaneously.