Merge pull request expressjs#69 from stevenp/master

Update README to fix incorrect example

README.md

@@ -92,7 +92,7 @@ var whitelist = ['http://example1.com', 'http://example2.com'];
 var corsOptions = {
   origin: function(origin, callback){
     var originIsWhitelisted = whitelist.indexOf(origin) !== -1;
-    callback(null, originIsWhitelisted);
+    callback(originIsWhitelisted ? null : 'Bad Request', originIsWhitelisted);
   }
 };