Add loading state to containers show more button

We lacked a loading state on our "show more" buttons for connections that are slow to get our content. Here's a cool one. Not too gimmicky I hope!

The animated gif does not do it justice, but here is what it's kind of supposed to look like:

![loader2](https://f.cloud.github.com/assets/85783/2346717/2dbe9914-a545-11e3-8976-44bb1b30e019.gif)