add some visualization effect on demo page

go and visit http://host:port/demo/demo-items and click one of the item, then click 'Start' button, and countdown begin!

![asdfasfd](https://cloud.githubusercontent.com/assets/2887655/4007853/8f5c679e-29cc-11e4-8f75-753cf39788f0.jpg)

try copy the url to a new tab and see the same countdown is progressing!