chore(package): update async to version 3.0.1

Author: greenkeeper[bot]

package.json

@@ -27,7 +27,7 @@
   },
   "homepage": "https://github.com/yourtion/express-coroutine#readme",
   "devDependencies": {
-    "async": "^2.6.0",
+    "async": "^3.0.1",
     "body-parser": "^1.18.2",
     "coveralls": "^3.0.0",
     "eslint": "^5.0.1",