Update constraint

Author: enumag

composer.json

@@ -31,7 +31,7 @@
 		"nette/http": "^2.4.7@dev",
 		"tracy/tracy": "^2.4@dev",
 
-		"symfony/event-dispatcher": "^3.0",
+		"symfony/event-dispatcher": "^3.0 || ^4.0",
 
 		"nette/tester": "~1.7"
 	},