Factor blob and blame.

Philosophy: blame is just a type of view for a blob. There is even a toggle button to go between both.

This PR factors:

- the filename holder on blame and blob views
- controller logic for blame which is identical for blame by moving `blame` into the blob controller

and it makes the following UI modifications which increases uniformity between blobs and blames:

- show the branch / path breadcrumb and last commit to the top of the blame
- remove the "blame view" title, since this is already obvious from the view itself, and from the "normal view" toggle button. Same rationale why the show view does not have a "Show view" title.

New:

![screenshot from 2014-09-28 00 18 17 blob blame new](https://cloud.githubusercontent.com/assets/1429315/4432445/f8bda826-4694-11e4-8088-3301225af0f1.png)

Old:

![screenshot from 2014-09-28 00 18 32 blob blame old](https://cloud.githubusercontent.com/assets/1429315/4432444/f0f9013a-4694-11e4-92b9-6f35d72a6005.png)