More visibility to when an element is zoomed and made it easier to remove a zoom object

* Added class to parent element so it is apparent that the element is zoomed
* if the parent element has a [data-zoom='img.png'] attribute it will be loaded as the zoomed image
* added a namespace to each of the event handlers so we can destroy everything easily by calling .unbind('click.zoom mouseenter.zoom mousemove.zoom mouseleave.zoom mousedown.click').find('.zoomImg').remove();

I didn't minify this as I am not sure what you are currently using.