made close() aware of settings.speed and settings.transition

I am working on an app that is doing *a lot* of DOM manipulation and wanted to reduce the load by specifying `{speed: 0, transition: "none"}`. This works when colorbox is first displayed, but `close()` is hardcoded to fadeOut. I modified `close()` so that it will obey settings.speed on the fadeOut, and not fadeOut at all if `settings.transition === "none"`