src/demo/demo.htm is broken

[iurisilvio]

Issues #18 and #19 are related to the same problem. The demo.htm file has a broken example. It works only with items_per_page=1, so it proves almost nothing about this plugin and gives trouble to any javascript beginner.

It is easy to fix that, I created a gist about it, just to show how it should be done. https://gist.github.com/379ec54bced24e079731