add support of symfony 4 (#993)

* add support of symfony 4

composer.json

@@ -25,12 +25,12 @@
         "sonata-project/doctrine-extensions": "^1.0",
         "sonata-project/easy-extends-bundle": "^2.2",
         "swiftmailer/swiftmailer": "^4.3 || ^5.0 || ^6.0",
-        "symfony/console": "^2.8 || ^3.2",
-        "symfony/form": "^2.8 || ^3.2",
-        "symfony/http-foundation": "^2.8 || ^3.2",
+        "symfony/console": "^2.8 || ^3.2 || ^4.0",
+        "symfony/form": "^2.8 || ^3.2 || ^4.0",
+        "symfony/http-foundation": "^2.8 || ^3.2 || ^4.0",
         "symfony/security-acl": "^2.8 || ^3.0",
-        "symfony/security-core": "^2.8 || ^3.2",
-        "symfony/translation": "^2.8 || ^3.2"
+        "symfony/security-core": "^2.8 || ^3.2 || ^4.0",
+        "symfony/translation": "^2.8 || ^3.2 || ^4.0"
     },
     "require-dev": {
         "doctrine/orm": "^2.0",
@@ -42,7 +42,7 @@
         "sonata-project/block-bundle": "^3.2",
         "sonata-project/google-authenticator": "^1.0 || ^2.0",
         "sonata-project/seo-bundle": "^2.0",
-        "symfony/phpunit-bridge": "^3.3"
+        "symfony/phpunit-bridge": "^4.0"
     },
     "suggest": {
         "friendsofsymfony/rest-bundle": "For using the public API methods.",