Expeimental symfony 4 support

.travis.yml

@@ -14,6 +14,7 @@ env:
   - SYMFONY_VERSION=2.7.*
   - SYMFONY_VERSION=2.8.*
   - SYMFONY_VERSION=3.0.* # Does not work with php below 5.5
+  - SYMFONY_VERSION=4.0.*
 
 cache:
   directories:

composer.json

@@ -13,7 +13,7 @@
     ],
     "require": {
         "php": ">=5.6",
-        "symfony/event-dispatcher": "~2.3|~3.0"
+        "symfony/event-dispatcher": "~2.3|~3.0|~4.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~3.7",