Add curated lists

https://www.pivotaltracker.com/n/projects/1110932

This ticket adds the ability to curate content tagged to a specialist sector into lists.

The lists can be ordered, as can the content within the lists.

The layout and interaction is generally good but could doubtless benefit from exposure to user research and further iteration.

![screenshot 2014-08-18 11 37 39](https://cloud.githubusercontent.com/assets/109225/3950332/bbfb04e2-26c3-11e4-94c7-44f3bf58d126.png)