Options: Height to Width Ratio

Added a Height to Width Ratio to the list of options (Width/Height). A 0.5 ratio would be used for an image that is twice as large as it's height. Default is 1 (square images). I guess we could switch it around (Height/Width (?)). I don't really mind. As long as we can use non-square thumbnails..!

I think this jQuery plugin is great but this really simple change would make it even better IMO.