[Translation] Ability to format a message catalogue without dumping it.

components/translation/custom_formats.rst

@@ -85,7 +85,7 @@ will save a few lines::
 
     class MyFormatDumper extends FileDumper
     {
-        protected function format(MessageCatalogue $messages, $domain = 'messages')
+        public function formatCatalogue(MessageCatalogue $messages, $domain, array $options = array())
         {
             $output = '';
 
@@ -102,7 +102,14 @@ will save a few lines::
         }
     }
 
-The :method:`Symfony\\Component\\Translation\\Dumper\\FileDumper::format`
+.. versionadded:: 2.8
+    The ability to format a message catalogue without dumping it was introduced in Symfony 2.8.
+
+.. tip::
+
+    To format a message catalogue without dumping it into files use the ``formatCatalogue`` method.
+
+The :method:`Symfony\\Component\\Translation\\Dumper\\FileDumper::formatCatalogue`
 method creates the output string, that will be used by the
 :method:`Symfony\\Component\\Translation\\Dumper\\FileDumper::dump` method
 of the FileDumper class to create the file. The dumper can be used like any other
@@ -116,4 +123,3 @@ YAML file are dumped into a text file with the custom format::
 
     $dumper = new MyFormatDumper();
     $dumper->dump($catalogue, array('path' => __DIR__.'/dumps'));
-