Merge branch '5.0'

* 5.0:
  Add notifier and string

Author: nicolas-grekas

composer.json

@@ -22,10 +22,12 @@
         "symfony/intl": "*",
         "symfony/mailer": "*",
         "symfony/monolog-bundle": "^3.1",
+        "symfony/notifier": "*",
         "symfony/orm-pack": "*",
         "symfony/process": "*",
         "symfony/security-bundle": "*",
         "symfony/serializer-pack": "*",
+        "symfony/string": "*",
         "symfony/translation": "*",
         "symfony/twig-pack": "*",
         "symfony/validator": "*",