Adds merge file collection functionality

Fixes #197 Note requires a file collection merge index to see functionality

![screen shot 2014-06-04 at 4 20 02 pm](https://cloud.githubusercontent.com/assets/1656824/3181439/fd6e2374-ec3e-11e3-9120-8cc127f0ba46.png)

![screen shot 2014-06-04 at 4 22 22 pm](https://cloud.githubusercontent.com/assets/1656824/3181449/2530849c-ec3f-11e3-9c6b-9dc7217fed46.png)

![screen shot 2014-06-04 at 4 22 32 pm](https://cloud.githubusercontent.com/assets/1656824/3181453/33aa34fa-ec3f-11e3-8e4d-100ee3f00751.png)