Mobile styling fixes

This pull request fixes issues for displaying the site on a mobile device, including:

- On Chrome for android the font weight high enough to render titles as bold. 
- On small screens images rendered outside of the bounds of the article. Max widths fix this
![screen shot 2014-03-18 at 22 03 01](https://f.cloud.github.com/assets/1446145/2454343/1bcc9b68-aee9-11e3-87eb-4c66b9ebf413.png)