require_oauth decorator was always succeeding.

verify_request() returns a tuple of (valid, oauth_request). The code was
treating it as if it returned just a bool, and since the never-empty
tuple was always truthy, requests always seemed to work.

Fixes ib-lundgren/flask-oauthprovider/#3
Merge pull request #5 from datalogics-kam/fix-require-oauth

require_oauth decorator was always succeeding.