Bump debug from 2.2.0 to 4.1.1 in /demo/2015.12.23-session

Bumps [debug](https://github.com/visionmedia/debug) from 2.2.0 to 4.1.1.
- [Release notes](https://github.com/visionmedia/debug/releases)
- [Commits](debug-js/debug@2.2.0...4.1.1)

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

Author: dependabot[bot]

demo/2015.12.23-session/package.json

@@ -8,7 +8,7 @@
   "dependencies": {
     "body-parser": "~1.13.2",
     "cookie-parser": "~1.3.5",
-    "debug": "~2.2.0",
+    "debug": "~4.1.1",
     "express": "~4.13.1",
     "express-session": "^1.12.1",
     "jade": "~1.11.0",