Duplicate tags now have their section in brackets

![screen shot 2014-10-02 at 15 16 49](https://cloud.githubusercontent.com/assets/2236852/4492135/c788a3e8-4a3e-11e4-9ddd-544a8e6a00cf.png)

There are sometimes duplicate tag names with different associated sections. If two tags with the same name are applied to a story then their parent section is now displayed in brackets.