loading on dynamic elements 

nice plugin, but doesn't work on dynamic elements

it would be great to specify jquery elements that are dyanmically added.
You could add a "delegate" or parent option which would accept a selector.

```
$('#threads').loading({
    parent: '#threadsContainer'
});
```

when 'close' method is triggered, the plugin will look for the newly added #threads wrapped in #threadsContainer
