Improve photo browser caption text.

* Decrease size of title.
* Increase size of caption.
* Use brand fonts.

https://app.asana.com/0/21460959388827/18997455830385

![screen shot 2014-12-11 at 16 46 12](https://cloud.githubusercontent.com/assets/4643064/5398940/a18a00c2-815e-11e4-8410-7901cd2967b7.png)
![screen shot 2014-12-11 at 16 47 47](https://cloud.githubusercontent.com/assets/4643064/5398934/9ada6776-815e-11e4-9051-1199cced98f9.png)