Merge pull request #235 from postmanlabs/revert-234-greenkeeper/async-3.0.1

Revert "Update async to the latest version 🚀"

Author: codenirvana

package-lock.json

@@ -26,7 +26,7 @@
   "license": "Apache-2.0",
   "devDependencies": {
     "ajv": "6.10.0",
-    "async": "3.0.1",
+    "async": "2.6.1",
     "browserify": "16.2.3",
     "chai": "4.2.0",
     "chalk": "2.4.2",