fix: package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/npm:debug:20170905
- https://snyk.io/vuln/npm:fresh:20170908
- https://snyk.io/vuln/npm:mime:20170907
- https://snyk.io/vuln/npm:ms:20170412

package.json

@@ -24,7 +24,7 @@
     "ejs": "1.0.0",
     "ejs-locals": "1.0.2",
     "errorhandler": "1.2.0",
-    "express": "4.12.4",
+    "express": "4.16.0",
     "express-fileupload": "0.0.5",
     "express-session": "^1.17.2",
     "file-type": "^8.1.0",