Handle HttpResponses returned by the pipeline

[lanterno]

Not sure if there's an alternative for this so i thought I'd ask and show you how I'd do this is the same time.
One of the most important use cases on the pipeline it to return HttpResponses in case or errors or facing missing data like if your facebook uses a phone number with no email address.
If you read this part in the documentation, you'll find that django-social-auth was built with that in mind
http://psa.matiasaguirre.net/docs/developer_intro.html#understanding-the-pipeline
Anyway, this case wasn't handled in the BaseSocialAuthView so I thought I'd change that. :)

[coveralls]

Coverage decreased (-0.4%) to 94.175% when pulling 2078fa3 on zee93:master into 7ae6986 on st4lk:master.

[coveralls]

Coverage increased (+0.08%) to 94.66% when pulling c0faddd on zee93:master into 7ae6986 on st4lk:master.

[st4lk]

Thanks Ahmed!

[st4lk]

Now in pypi v0.5.0