Fix link to Dive Into Python 3

Author: puppe

docs/intro/learning.rst

@@ -39,7 +39,7 @@ Dive Into Python 3 is a good book for those ready to jump in to Python 3. It's
 a good read if you are moving from Python 2 to 3 or if you already have some
 experience programming in another language.
 
-    `Dive Into Python 3 <http://diveintopython3.ep.io/>`_
+    `Dive Into Python 3 <http://www.diveinto.org/python3/>`_
 
 Think Python: How to Think Like a Computer Scientist
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~