examples: use http-errors to create errors

examples/params/index.js

@@ -4,6 +4,7 @@
  * Module dependencies.
  */
 
+var createError = require('http-errors')
 var express = require('../../');
 var app = module.exports = express();
 
@@ -17,14 +18,6 @@ var users = [
   , { name: 'bandit' }
 ];
 
-// Create HTTP error
-
-function createError(status, message) {
-  var err = new Error(message);
-  err.status = status;
-  return err;
-}
-
 // Convert :to and :from to integers
 
 app.param(['to', 'from'], function(req, res, next, num, name){