Facebook comments integration on Docs and Blog

Blog:
![image](https://f.cloud.github.com/assets/197597/616524/8ed1a832-ce71-11e2-98ae-2bb4dae6f3c6.png)

Docs:
![image](https://f.cloud.github.com/assets/197597/616531/c6efd540-ce71-11e2-8686-e50d5cde9d39.png)