Add links to old and new package names

This will render for users who look at pep8 1.7.x's documentation
and hopefully help inform them that pep8 is deprecated and now
replaced by pycodestyle.

Closes #602

docs/index.rst

@@ -5,7 +5,8 @@ pep8's documentation
 
 .. note::
 
-    This package used to be called ``pep8`` but was renamed to ``pycodestyle``
+    This package used to be called `pep8 <https://pypi.python.org/pypi/pep8/1.7.0>`_ 
+    but was renamed to `pycodestyle <https://pypi.python.org/pypi/pycodestyle/2.2.0>`_
     to reduce confusion. Further discussion can be found `in the issue where
     Guido requested this
     change <https://github.com/PyCQA/pycodestyle/issues/466>`_, or in the