examples: add missing cookie-session module

fixes #2589

examples/cookie-sessions/index.js

@@ -2,6 +2,7 @@
  * Module dependencies.
  */
 
+var cookieSession = require('cookie-session');
 var express = require('../../');
 
 var app = module.exports = express();

package.json

@@ -63,6 +63,7 @@
     "body-parser": "~1.12.0",
     "connect-redis": "~2.2.0",
     "cookie-parser": "~1.3.4",
+    "cookie-session": "~1.1.0",
     "express-session": "~1.10.3",
     "jade": "~1.9.2",
     "method-override": "~2.3.1",