Added driver support for Rack::Request

Ahoy,

I added driver support for Rack::Request.

-Jonnie

**update** - added headers test. missed those the first time, but all was good.

![big-32](https://f.cloud.github.com/assets/158963/25833/e6d18a0e-4af8-11e2-8ab5-423fb53aa71d.gif)