Fixed #739 Made minor CSS fixes to /guide/

Trying to resolve https://openhatch.org/bugs/issue739. 
Let me know how I can improve this pull request (PR). I mostly followed pythonian4000's suggestions in comments of the issue tracker. 

Please note that the below BEFORE vs. AFTER screenshots are local instances of oh-mainline running from localhost:800 on MacOX. 

BEFORE: 
![openhatch-before](https://f.cloud.github.com/assets/954858/1749789/96fc1ffa-653f-11e3-93c3-b4a17eb236c5.png)


AFTER: I centered the contact us link in left sidebar. The bullet points fit inside the gray box.
![openhatch-issue 739](https://f.cloud.github.com/assets/954858/1749787/79715ab8-653f-11e3-9303-9528d3d83b07.png)