Bump express from 4.16.2 to 4.17.3

Bumps [express](https://github.com/expressjs/express) from 4.16.2 to 4.17.3.
- [Release notes](https://github.com/expressjs/express/releases)
- [Changelog](https://github.com/expressjs/express/blob/master/History.md)
- [Commits](https://github.com/expressjs/express/compare/4.16.2...4.17.3)

---
updated-dependencies:
- dependency-name: express
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -26,7 +26,7 @@
     "bluebird": "^3.5.1",
     "body-parser": "^1.18.2",
     "connect": "^3.6.5",
-    "express": "^4.16.2",
+    "express": "^4.17.3",
     "mongodb": "^3.1.13",
     "mongoose": "^5.7.5",
     "passport": "^0.4.0",