Added show more button atom.

Amazing new show more button styles:
![screen shot 2014-10-13 at 17 23 35](https://cloud.githubusercontent.com/assets/2579465/4627512/fe425fe0-538b-11e4-9471-579d98440702.png)

this is all very specific to using `i-plus-neutral1` icon. fine for now, as we don't have a `pasteup-icons`, but will need revisiting