fix(package): update async to version 3.1.0

Closes #22

Author: greenkeeper[bot]

package.json

@@ -35,7 +35,7 @@
   "homepage": "https://github.com/pigcan/node-isimulator",
   "dependencies": {
     "appium-ios-simulator": "^2.5.0",
-    "async": "^2.0.0-rc.6",
+    "async": "^3.1.0",
     "babel-runtime": "^6.9.2",
     "bplist-parser": "^0.1.1",
     "chalk": "^2.2.2",