chore(package): update express to version 4.17.1

Closes #5

Author: greenkeeper[bot]

package.json

@@ -22,7 +22,7 @@
   },
   "dependencies": {},
   "devDependencies": {
-    "express": "~4.15.2",
+    "express": "~4.17.1",
     "compression": "^1.3.0",
     "serve-static": "^1.8.0",
     "grunt": "^1.0.1",