Updading social_auth_app_django to 3.x to handle new Google API for oauth2....

Updading social_auth_app_django to 3.x to handle new Google API for oauth2. The Google+ API is going away.

requirements.txt

@@ -23,7 +23,7 @@ responses==0.9.0
 
 flake8
 
-social_auth_app_django==2.1.0
+social_auth_app_django==3.1.0
 django-tables2==1.21.1
 django-filter==1.1.0
 django_select2==6.0.1