jQuery 1.8 support & wrapper element support

I made some modifications to this library for the project I'm working with, and I thought they might be useful for you. First commit is a tweak to support jQuery 1.8, since it doesn't support the method _super() yet. Second commit is addition of "useParentForScrolling" as an option, for situations where the scrolling div needs to be the parent of div with selectable items in it, like this: http://stackoverflow.com/questions/2330773/jquery-ui-selectable-plugin-make-scroll-bar-not-selectable-when-div-overflows