upgrade to CE v7.5.1 and shell v2.2.0

Upgraded the repo to the newest version of GitLab (7.5.1). Tested the Dockerfile and successfully built the image and booted up.
![screen shot 2014-11-22 at 5 24 02 pm](https://cloud.githubusercontent.com/assets/449321/5156047/7e273cd6-726c-11e4-88c2-6ffe93724ece.png)