Sets release date for 3.0.6

Changelog

@@ -13,7 +13,7 @@ If you're looking for versions prior to 3.x you should see :ref:`history`.
 
 3.0.6
 =====
-:release-date: 2012-09-XX XX:XX X.M BST
+:release-date: 2012-09-17 11:00 P.M BST
 
 - Now depends on kombu 2.4.0