fix(package): update es6-promise to version 4.2.2

Closes #225

Author: greenkeeper[bot]

package.json

@@ -15,7 +15,7 @@
   },
   "dependencies": {
     "@types/node": "^8.0.53",
-    "es6-promise": "4.1.1",
+    "es6-promise": "4.2.2",
     "form-data": "2.3.1",
     "isomorphic-fetch": "2.2.1",
     "object-assign": "4.1.1",