Redesign the SkyLabels landing page

* Switch to using Middleman for development
* Add new "try it out" styles
* Update to newest version of SkyLabels
* Add 4 sample websites that people can see
* Update visual style

### Files that probably need the most feedback :D

source/layouts/layout.erb
source/index.html.erb
source/stylesheets/**

See the animations in the demo here: http://cl.ly/1M0B0W0R0P45

![screen shot 2014-11-21 at 3 23 06 pm](https://cloud.githubusercontent.com/assets/22394/5148982/5774e9ec-7192-11e4-9cd9-5c9304899a42.png)
maybe shorthand this, ```margin: 0 auto;```