Allow individual bridges, bundles and components to be used with 4.0

Author: dunglas

composer.json

@@ -28,7 +28,7 @@
         "symfony/polyfill-intl-icu": "~1.0"
     },
     "require-dev": {
-        "symfony/filesystem": "~2.8|~3.0"
+        "symfony/filesystem": "~2.8|~3.0|~4.0.0"
     },
     "suggest": {
         "ext-intl": "to use the component with locales other than \"en\""