Moved versionadded block to the top.

Author: derrabus

components/class_loader/psr4_class_loader.rst

@@ -4,12 +4,12 @@
 The PSR-4 Class Loader
 ======================
 
-Libraries that follow the `PSR-4`_ standard can be loaded with the ``Psr4ClassLoader``.
-
 .. versionadded:: 2.5
     The :class:`Symfony\\Component\\ClassLoader\\Psr4ClassLoader` was
     introduced in Symfony 2.5.
 
+Libraries that follow the `PSR-4`_ standard can be loaded with the ``Psr4ClassLoader``.
+
 .. note::
 
     If you manage your dependencies via Composer, you get a PSR-4 compatible