Provide additional data for images

It would be great to provide a data object for each image, rather than just a url.
For example, I'd like to add a class to each image so that I can overlay info/style them.
Might be useful to pass in a thumbnail while loading etc.
Something like

```
ameLightbox.show([{
  url: "",
  thumbnailUrl: "',
  class: ['my-class']
}])

```

Cool plugin, thanks for sharing it.