Make the entire squares clickable

Minor styling changes and make the entire squares clickable instead of child anchor elements.

Also added `.selected` styling which seems to be missing from the repo: 

![screen shot 2014-05-22 at 10 57 37](https://cloud.githubusercontent.com/assets/938453/3049348/dc784e66-e15c-11e3-957a-235b596bc6dc.png)