Clarify tip for creating a new AppBundle

The previous description was not quite right, since an AppBundle can
also be there in versions before 2.6.

Author: xelaris

best_practices/creating-the-project.rst

@@ -152,9 +152,9 @@ that follows these best practices:
 
 .. tip::
 
-    If you are using Symfony 2.6 or a newer version, the ``AppBundle`` bundle
-    is already generated for you. If you are using an older Symfony version,
-    you can generate it by hand executing this command:
+    If you are using an existing Symfony installation, which doesn't come with a
+    pre-generated ``AppBundle``, you can generate it by hand executing this 
+    command:
 
     .. code-block:: bash