[Security] Add ExpressionLanguage to require-dev.

Author: realityking

composer.json

@@ -20,6 +20,7 @@
     },
     "require-dev": {
         "symfony/event-dispatcher": "~2.1",
+        "symfony/expression-language": "~2.4",
         "symfony/http-foundation": "~2.4",
         "symfony/validator": "~2.2",
         "psr/log": "~1.0",