Merge pull request #223 from adamchainz/readthedocs.io

Convert readthedocs links for their .org -> .io migration for hosted projects

README.rst

@@ -52,7 +52,7 @@ Django to perform an ``INNER JOIN`` to fetch the model fields from the database.
 While taking this in mind, there are valid reasons for using subclassed models.
 That's what this library is designed for!
 
-For more information, see the `documentation at Read the Docs <https://django-polymorphic.readthedocs.org/>`_.
+For more information, see the `documentation at Read the Docs <https://django-polymorphic.readthedocs.io/>`_.
 
 License
 =======

docs/third-party.rst

@@ -10,7 +10,7 @@ However, they require more setup than standard models. That's become:
 * The children models are not registered in the admin site.
   You will therefore need to manually register them to django-reversion_.
 * Polymorphic models use `multi-table inheritance <https://docs.djangoproject.com/en/dev/topics/db/models/#multi-table-inheritance>`_.
-  See the `reversion documentation <http://django-reversion.readthedocs.org/en/latest/api.html#multi-table-inheritance>`_
+  See the `reversion documentation <https://django-reversion.readthedocs.io/en/latest/api.html#multi-table-inheritance>`_
   how to deal with this by adding a ``follow`` field for the primary key.
 * Both admin classes redefine ``object_history_template``.