Prevented gist timestamp from overlapping with code box.

Looooooong gist title was making its timestamp to overlap with code box.

![Before](https://f.cloud.github.com/assets/498635/1848590/94ab77ba-7691-11e3-9cea-a774ef4dea08.png)

Fixed the issue applying clearfix to gist titles.

![After](https://f.cloud.github.com/assets/498635/1848603/28e5e398-7692-11e3-9fd5-7a0dc1a11759.png)