Merge pull request #1207 from erkarl/master

Updated OAuth2 authentication docs.

docs/api-guide/authentication.md

@@ -265,6 +265,12 @@ This authentication class depends on the optional [django-oauth2-provider][djang
         'provider.oauth2',
     )
 
+Then add `OAuth2Authentication` to your global `DEFAULT_AUTHENTICATION` setting:
+
+    'DEFAULT_AUTHENTICATION_CLASSES': (
+        'rest_framework.authentication.OAuth2Authentication',
+    ),
+
 You must also include the following in your root `urls.py` module:
 
     url(r'^oauth2/', include('provider.oauth2.urls', namespace='oauth2')),