Series labelling

This adds labelling to the top of all content that belongs in a series.

### Mobile
![screenshot from 2014-04-08 12 39 18](https://cloud.githubusercontent.com/assets/80089/2642987/9ec38566-bf12-11e3-8657-01da80d58fc0.png)

### Desktop
![screenshot from 2014-04-08 12 39 43](https://cloud.githubusercontent.com/assets/80089/2642988/a34a83be-bf12-11e3-87d1-9b3ea8bce7a5.png)