Refactor authorize method to be aware of 3-legged or 2-legged auth
Refactor authorize method to be aware of 3-legged or 2-legged auth

Break up signature verification its respective steps so they can be
applied or not if we're using 3-legged or 2-legged auth.

If we are using 2-legged auth, we return the consumer key as the user
id on a successful authorize call.

ciaranj/connect-auth,bottlenose-inc/connect-auth