Replace second introduction item with illustration

![illustration](https://cloud.githubusercontent.com/assets/5547897/5134716/70fc7024-70c5-11e4-8ecb-e87a712b964e.png)

![illustration2](https://cloud.githubusercontent.com/assets/5547897/5134717/70fcd5c8-70c5-11e4-8823-ff5d1fc22ea2.png)