chore(package): update supertest to version 4.0.1

Closes #54

Author: greenkeeper[bot]

package.json

@@ -26,7 +26,7 @@
     "chai": "^4.1.2",
     "eslint": "^4.7.2",
     "mocha-eslint": "^4.1.0",
-    "supertest": "^3.0.0"
+    "supertest": "^4.0.1"
   },
   "scripts": {
     "start": "yarn global add nodemon; nodemon server.js",