Prevented gist timestamp from overlapping with code box.

Looooooong gist title was making its timestamp to overlap with code box.

![screen shot 2014-01-06 at 14 09 51](https://f.cloud.github.com/assets/498635/1848590/94ab77ba-7691-11e3-9cea-a774ef4dea08.png)

Fixed the issue applying clearfix to gist titles.