Added default for HttpMock
diff --git a/apiclient/model.py b/apiclient/model.py
index 68da13e..58cd624 100644
--- a/apiclient/model.py
+++ b/apiclient/model.py
@@ -2,7 +2,7 @@
 #
 # Copyright 2010 Google Inc. All Rights Reserved.
 
-"""Model objects for requests and responses
+"""Model objects for requests and responses.
 
 Each API may support one or more serializations, such
 as JSON, Atom, etc. The model classes are responsible