Nicer homepage.

* Add img-responsive class. 
* Replace `img-circle` with `img-rounded`. 
* Remove unnecessary CSS rules.

Old:
![screen shot 2013-11-20 at 11 13 06 pm](https://f.cloud.github.com/assets/193112/1583090/a7d15890-51f8-11e3-9c6c-b74c29ccc38a.png)

New:
![screen shot 2013-11-20 at 11 23 57 pm](https://f.cloud.github.com/assets/193112/1583091/aacf46ec-51f8-11e3-9317-a7c35b88b8bb.png)