Move date submitted to header section

This PR moves the date submitted on a submission page to the header part, where the author is already displayed. This not only makes more sense textually "submitted by <...> at <...>", it also cleans up the page to have the actual code appear more to the top of the page.

Before:
![screen shot 2014-11-22 at 10 31 49](https://cloud.githubusercontent.com/assets/135246/5153654/d49f76da-7232-11e4-9cc9-eefa36c9428d.png)

After:
![screen shot 2014-11-22 at 10 31 04](https://cloud.githubusercontent.com/assets/135246/5153653/d1046044-7232-11e4-877f-6721f9955103.png)