More galleries container - series lozenges

![screen shot 2014-09-23 at 14 37 13](https://cloud.githubusercontent.com/assets/2236852/4372732/c7d540d2-4326-11e4-8ee8-825a64e5e133.png)

Added a hard-coded list of gallery series that show in the 'more galleries' container at the bottom of gallery posts. 

Number of other changes:
- Changed the colours of borders on the 'more' button for tags on features & comment articles
- Cleaned up classes made redundant by the submeta work by @mattosborn (.social__head)
- One IE bug fix for the more button for tags in IE8/9
js-* prefixed classes are meant exclusively for use in javascript (to keep a clear separation between behaviour and appearance)