Use icons for Flappy blocks

![image](https://cloud.githubusercontent.com/assets/206973/2897157/cbcd8fde-d579-11e3-903d-ddb6a0442c55.png)

![image](https://cloud.githubusercontent.com/assets/206973/2897161/d2fe54fa-d579-11e3-92af-46c89c46a0a4.png)

![image](https://cloud.githubusercontent.com/assets/206973/2897162/d8dc9d46-d579-11e3-8140-4aff028e6dc6.png)