Merge branch '2.8'

Conflicts:
	src/Symfony/Bridge/PhpUnit/composer.json
	src/Symfony/Component/Serializer/composer.json

Author: Tobion

composer.json

@@ -17,7 +17,7 @@
     ],
     "require": {
         "php": ">=5.5.9",
-        "symfony/polyfill-php54": "~1.0"
+        "symfony/polyfill-php55": "~1.0"
     },
     "require-dev": {
         "symfony/yaml": "~2.8|~3.0",