fix(package): update express to version 4.17.1

Closes #27

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
     "cors": "^2.8.4",
     "debug": "~3.1.0",
     "dotenv-extended": "^2.2.0",
-    "express": "~4.16.0",
+    "express": "~4.17.1",
     "http-errors": "~1.7.0",
     "jade": "~1.11.0",
     "morgan": "~1.9.0",