chore(package): update supertest to version 4.0.1

Closes #46

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "jest": "^23.6.0",
     "nodemon": "^1.18.5",
     "nsp": "^3.1.0",
-    "supertest": "^3.3.0",
+    "supertest": "^4.0.1",
     "ts-jest": "^23.10.4",
     "ts-node": "^7.0.1",
     "tslint": "^5.11.0",