adds twitter widget

Hi,

I just had an idea and thought I'd cook up a small PR to open up the discussion, instead of just opening an Issue.
I think it would be added value to have a small Twitter widget that shows #pairwithme tweets, so you can instantly see if anyone's available at the moment.

Never mind the style mangling, just want to gauge interest :)

Here's a screenshot of my change:
![Twitter Widget](http://hostr.co/file/hoy09DfQEkqd/Screen-Shot-2013-05-14-at-14.00.47.png)