Do not insert a comma after the Authorization header for OAuth1.0 Resource Owners

[According to the OAuth1.0 standard](http://oauth.net/core/1.0/#auth_header) there should be no comma after `Authorization: OAuth` in the Authorization header. This is not stated specifically in the standard but the example it provides says so:

    Authorization: OAuth realm="http://sp.example.com/",
    oauth_consumer_key="0685bd9184jfhq22",
    ...

Currently there is a comma after `Authorization: OAuth`:

    Authorization: OAuth, realm="http://sp.example.com/",
    oauth_consumer_key="0685bd9184jfhq22",
    ...

This comma breaks Google's implementation of OAuth 1.0, which returns the following error:

    parameter_absent
    oauth_parameters_absent:oauth_consumer_key&oauth_signature_method&
    oauth_signature&oauth_timestamp&oauth_nonce&scope

This PR fixes this issue.