Add social media buttons to the front page. Fixes #59.

![social](https://f.cloud.github.com/assets/167819/2107447/067e808e-8fca-11e3-86de-eda73bcd24c3.png)
![social-blocked](https://f.cloud.github.com/assets/167819/2107434/ef3dc628-8fc9-11e3-8cd2-aab9d0603b78.png)