V2 Request - Ajax Loading Slides (after the first).

Issue Summary

Thanks for the work on this great module.

I've run into issues where clients load lots of images into their slideshows making load times on mobile pretty terrible via 3G. It would be great to get all those images to lazy load after the document initializes. Perhaps load just the first image normally, and then Ajax load the rest.

The v2 branch has the slider.addSlide method which I think should make it possible to ajax load all the slides after the first. My JS skills are not very strong, but I was thinking perhaps you could trim the array of content passed by views to flexslider to show only the first item, and then loop the rest though slider.addSlide method.

I'm not sure if it's possible but I could see there being a good argument to ajax load even the first slide as the "apparent speed" of the site would be increased.

Here's a related flexslider link on github https://github.com/woothemes/FlexSlider/issues/310