Bump morgan from 1.6.1 to 1.9.1 in /demo/2015.12.23-session

Bumps [morgan](https://github.com/expressjs/morgan) from 1.6.1 to 1.9.1.
- [Release notes](https://github.com/expressjs/morgan/releases)
- [Changelog](https://github.com/expressjs/morgan/blob/master/HISTORY.md)
- [Commits](expressjs/morgan@1.6.1...1.9.1)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

demo/2015.12.23-session/package.json

@@ -12,7 +12,7 @@
     "express": "~4.13.1",
     "express-session": "^1.12.1",
     "jade": "~1.11.0",
-    "morgan": "~1.6.1",
+    "morgan": "~1.9.1",
     "serve-favicon": "~2.3.0"
   }
 }