fix: docs/presentation/package.json to reduce vulnerabilities (#157)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/npm:fresh:20170908

docs/presentation/package.json

@@ -22,7 +22,7 @@
     "node": ">=4.0.0"
   },
   "dependencies": {
-    "express": "~4.14.0",
+    "express": "~4.15.5",
     "grunt-cli": "~1.2.0",
     "mustache": "~2.2.1",
     "socket.io": "^1.4.8"