Update readme.rst

The IRC link no longer works since the website has been updated.
diff --git a/readme.rst b/readme.rst
index 8628645..d768162 100644
--- a/readme.rst
+++ b/readme.rst
@@ -52,7 +52,7 @@
 -  `User Guide <http://codeigniter.com/user_guide/>`_
 -  `Community Forums <http://codeigniter.com/forums/>`_
 -  `Community Wiki <http://codeigniter.com/wiki/>`_
--  `Community IRC <http://codeigniter.com/irc/>`_
+-  `Community IRC <http://ellislab.com/codeigniter/irc>`_
 
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 Acknowledgement