[MR][Composer] added a required dependency to symfony/event-dispatche…

…r (Issue piece#4)

composer.json

@@ -16,7 +16,7 @@
         "php": ">=5.3.2",
         "piece/stagehand-fsm": ">=2.0.0",
         "symfony/config": ">=2.0.0",
-        "symfony/event-dispatcher": "~2.1"
+        "symfony/event-dispatcher": "~2.1",
         "symfony/http-foundation": ">=2.0.0",
         "symfony/yaml": ">=2.0.0"
     },