Add full-screen error to styleguide (bug 933314)

This branch adds a couple of example of full-screen error examples to the style-guide.
![firefox_os_simulator_and_simulator_dashboard_-_firefox_os](https://f.cloud.github.com/assets/1514/1447554/3e26f8e6-4249-11e3-9b9f-115e2586d943.png)