Update DNS component for required DNS fallback support

Author: clue

composer.json

@@ -28,7 +28,7 @@
     "require": {
         "php": ">=5.3.0",
         "evenement/evenement": "^3.0 || ^2.0 || ^1.0",
-        "react/dns": "dev-master#ae37876 as 1.7.0",
+        "react/dns": "^1.7",
         "react/event-loop": "^1.0 || ^0.5",
         "react/promise": "^2.6.0 || ^1.2.1",
         "react/promise-timer": "^1.4.0",