Adding an article to explain the 3.3 changes, and how to upgrade

Author: weaverryan

controller.rst

@@ -142,6 +142,8 @@ Add the ``use`` statement atop the ``Controller`` class and then modify
 That's it! You now have access to methods like :ref:`$this->render() <controller-rendering-templates>`
 and many others that you'll learn about next.
 
+.. _controller-abstract-versus-controller:
+
 .. tip::
 
     You can extend either ``Controller`` or ``AbstractController``. The difference

controller/service.rst

@@ -152,6 +152,8 @@ the route ``_controller`` value:
     fully-qualified class name (FQCN). See the
     `FrameworkExtraBundle documentation`_ for details.
 
+.. _controller-service-invoke:
+
 .. tip::
 
     If your controller implements the ``__invoke()`` method, you can simply

service_container.rst

@@ -117,6 +117,11 @@ in the container.
 Creating/Configuring Services in the Container
 ----------------------------------------------
 
+.. tip::
+
+    The recommended way of configuring services changed in Symfony 3.3. For a deep
+    explanation, see :doc:`/service_container/3.3-di-changes`.
+
 You can also organize your *own* code into services. For example, suppose you need
 to show your users a random, happy message. If you put this code in your controller,
 it can't be re-used. Instead, you decide to create a new class::