fix responsive blockquote

Blockquotes seem to run off the screen, while also widening the viewport.  This fixes that.

## Before

*(notice the dark gray to the right, representing the wide viewport, enabling horizontal scroll)*

![2014-02-20 at 10 01 pm](https://f.cloud.github.com/assets/401520/2227014/390f136a-9ab5-11e3-87e6-1bc18d6ccba8.png)

## After

![2014-02-20 at 9 59 pm](https://f.cloud.github.com/assets/401520/2227008/09630cde-9ab5-11e3-8484-01a175d8c1c2.png)