Allow emails to be responsive

:fork_and_knife: This removes the set width on the content container for mailers and sets a percentage based with and a max width and makes a few adjustments so everything looks ok at smaller sizes.

![screen shot 2014-06-24 at 11 33 44 am](https://cloud.githubusercontent.com/assets/316507/3373576/f6ab2d04-fbb4-11e3-96b3-aba666a168b6.png)