Removed BC slugifier package requirement

Author: wouterj

composer.json

@@ -13,8 +13,7 @@
     ],
     "require": {
         "php": "^5.5.9|^7.0",
-        "symfony/framework-bundle": "^2.8|^3.0",
-        "symfony-cmf/slugifier-api": "^1.0"
+        "symfony/framework-bundle": "^2.8|^3.0"
     },
     "require-dev": {
         "symfony/security-bundle": "^2.8|^3.0",