fix(package): update express to version 4.17.1

Closes #41

Author: greenkeeper[bot]

package.json

@@ -36,7 +36,7 @@
         "bluebird": "~3.5.4",
         "body-parser": "~1.19.0",
         "debug": "~4.1.1",
-        "express": "~4.16.4",
+        "express": "~4.17.1",
         "prom-client": "~11.3.0",
         "sinek": "~7.29.3"
     },