sf3 support

composer.json

@@ -12,8 +12,8 @@
     ],
     "require": {
         "php": ">=5.4",
-        "symfony/serializer": "~2.7",
-        "symfony/options-resolver": "~2.7"
+        "symfony/serializer": "<=3.0",
+        "symfony/options-resolver": "<=3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~4.4",