Layer selector + list of quakes

Adds a layer selector for map tiles and a list of displayed quakes if they number < 15.

Preview here: http://blooming-shore-3471.herokuapp.com/

![Screen Shot 2013-03-04 at 6 18 47 PM](https://f.cloud.github.com/assets/501816/217825/08f5b306-84f8-11e2-9a99-7fed4b8ae517.png)