Be a bit more strict

Author: wouterj

composer.json

@@ -14,7 +14,7 @@
     "require": {
         "php": "^5.3.9|^7.0",
         "symfony/framework-bundle": "^2.3",
-        "symfony-cmf/slugifier-api": "^1.0@dev"
+        "symfony-cmf/slugifier-api": "^1.0@rc"
     },
     "require-dev": {
         "symfony/security-bundle": "^2.1",