fix(package): update express to version 4.17.1

Closes #432

Author: greenkeeper[bot]

package.json

@@ -31,7 +31,7 @@
     "body-parser": "1.18.2",
     "cookie-parser": "1.4.3",
     "debug": "3.1.0",
-    "express": "4.16.2",
+    "express": "4.17.1",
     "express-graphql": "0.6.11",
     "graphql": "0.11.7",
     "joi": "12.0.0",