Override default request object name

Hi ForbesLindesay :) I thought this might be a useful feature for others as well - the ability to choose the name of the role user object attached to the request object. Passport has a similar function, which I find useful. If you are not crazy about this change, no problem, or if you would like me to make some adjustments before acceptance, please let me know. I am happy to do so. Thank you kindly for the great lib.
-porkchop