Flows no longer need to be saved between uses.

Also introduces util.positional declarations.

Reviewed in http://codereview.appspot.com/6441056/.

Fixes issue #136.
diff --git a/tests/test_oauth2client_jwt.py b/tests/test_oauth2client_jwt.py
index 65a3410..11162be 100644
--- a/tests/test_oauth2client_jwt.py
+++ b/tests/test_oauth2client_jwt.py
@@ -114,7 +114,7 @@
       ])
 
     contents = verify_id_token(jwt,
-        'some_audience_address@testing.gserviceaccount.com', http)
+        'some_audience_address@testing.gserviceaccount.com', http=http)
     self.assertEqual('billy bob', contents['user'])
     self.assertEqual('data', contents['metadata']['meta'])
 
@@ -126,7 +126,7 @@
       ])
 
     self.assertRaises(VerifyJwtTokenError, verify_id_token, jwt,
-        'some_audience_address@testing.gserviceaccount.com', http)
+        'some_audience_address@testing.gserviceaccount.com', http=http)
 
   def test_verify_id_token_bad_tokens(self):
     private_key = datafile('privatekey.p12')