`jQuery.easing` is currently passed 4 arguments: https://github.com/jquery/jquery/blob/0019a463bdcb81dc6ba3434505a45774ca27f363/src/effects/Tween.js#L35 @gnarf said it's a legacy behavior so maybe we should remove it? Thanks to @Mr21 for digging in.
