Merge pull request #1465 from dpursehouse/doc-netrc-authentication

Improve documentation of netrc authentication

docs/user/authentication.rst

@@ -32,6 +32,17 @@ Providing the credentials in a tuple like this is exactly the same as the
 ``HTTPBasicAuth`` example above.
 
 
+netrc Authentication
+~~~~~~~~~~~~~~~~~~~~
+
+If no authentication method is given with the ``auth`` argument, Requests will
+attempt to get the authentication credentials for the URL's hostname from the
+user's netrc file.
+
+If credentials for the hostname are found, the request is sent with HTTP Basic
+Auth.
+
+
 Digest Authentication
 ---------------------