Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

vendor/symfony/serializer/README.md

@@ -0,0 +1,15 @@
+Serializer Component
+====================
+
+With the Serializer component it's possible to handle serializing data structures,
+including object graphs, into array structures or other formats like XML and JSON.
+It can also handle deserializing XML and JSON back to object graphs.
+
+Resources
+---------
+
+You can run the unit tests with the following command:
+
+    $ cd path/to/Symfony/Component/Serializer/
+    $ composer install
+    $ phpunit