Update to stable reactphp/event-loop v1.2.0

Author: clue

composer.json

@@ -27,7 +27,7 @@
     ],
     "require": {
         "php": ">=5.3.8",
-        "react/event-loop": "dev-master#78f7f43 as 1.2.0",
+        "react/event-loop": "^1.2.0",
         "evenement/evenement": "^3.0 || ^2.0 || ^1.0"
     },
     "require-dev": {