Merge pull request #1464 from dpursehouse/document-none-not-sent

Fix #1322: Add note in docs about None not being sent as data

docs/user/quickstart.rst

@@ -71,6 +71,9 @@ You can see that the URL has been correctly encoded by printing the URL::
     >>> print r.url
     u'http://httpbin.org/get?key2=value2&key1=value1'
 
+Note that any dictionary key whose value is ``None`` will not be added to the
+URL's query string.
+
 
 Response Content
 ----------------