docs(intro):swap mailinglist with stackoverflow

Author: Byron

doc/source/intro.rst

@@ -90,9 +90,11 @@ Finally verify the installation by running the `nose powered <http://code.google
     
     $ nosetests
     
-Mailing List
-============
-http://groups.google.com/group/git-python
+Questions and Answers
+=====================
+Please use stackoverflow for questions, and don't forget to tag it with `gitpython` to assure the right people see the question in a timely manner.
+
+http://stackoverflow.com/questions/tagged/gitpython
 
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