Update supertest to the latest version 🚀 (#38)

* chore(package): update supertest to version 4.0.0

* chore(package): update lockfile package-lock.json

Author: greenkeeper[bot]

package-lock.json

@@ -38,7 +38,7 @@
     "mocha": "^6.0.0",
     "nyc": "^13.3.0",
     "sinon": "^7.2.4",
-    "supertest": "^3.4.2"
+    "supertest": "^4.0.0"
   },
   "dependencies": {}
 }