Remove the page about python memory management and its references

doc/tutorial/index.txt

@@ -71,6 +71,5 @@ Further readings
     ../extending/graphstructures 
     loading_and_saving
     aliasing
-    python-memory-management
     multi_cores
     faq_tutorial

doc/tutorial/python.txt

@@ -12,5 +12,3 @@ tutorials/exercises if you need to learn it or only need a refresher:
   * `Dive into Python <http://diveintopython.net/>`__
   * `Google Python Class <https://developers.google.com/edu/python/>`__
   * `Enthought Python course <https://training.enthought.com/?utm_source=academic&utm_medium=email&utm_campaign=EToD-Launch#/courses>`__ (free for academics)
-
-We have a tutorial on how :ref:`Python manages its memory <python-memory-management>`.