chore(package): update async to version 2.3.0 (#1807)

https://greenkeeper.io/

package.json

@@ -8,7 +8,7 @@
   },
   "license": "Apache-2.0",
   "devDependencies": {
-    "async": "~2.2.0",
+    "async": "~2.3.0",
     "babel": "~6.23.0",
     "babel-core": "~6.24.0",
     "babel-loader": "~6.4.1",