Update to Flask-OAuthlib 0.4.1 and oauthlib 0.6.0

Update to the Flask-OAuthlib 0.4.1 and oauthlib 0.6.0 combination; because *"Flask-OAuthlib is designed as a replacement for Flask-OAuth"* and that *"the client part of Flask-OAuthlib shares the same API as Flask-OAuth, which is pretty and simple"* (see https://flask-oauthlib.readthedocs.org/en/latest/ and https://github.com/lepture/flask-oauthlib).

Note that the previous/current Flask-OAuth 0.13 and oauth2 1.5 libraries haven't been updated for more than a year (see https://github.com/mitsuhiko/flask-oauth/releases and https://pypi.python.org/pypi/oauth2/).

Responses to http://stackoverflow.com/questions/15964268/flask-oauth-github-post-requests also suggested Flask-Rauth (see https://github.com/joelverhagen/flask-rauth) as an alternative to Flask-OAuthlib, but the same/similar API promise of Flask-OAuthlib made me follow up on that path first.

Why bother?  I noticed (but cannot reproduce in a reliable way) that sometimes a new user (via Google sign-in) got some kind of a URL as his/her Username... As said, I cannot reproduce, and it may even have been temporarily. But nevertheless, it got me wondering if the OAuth libraries were latest versions.