Added DOM cloning for state saving

When going in reverse, the animation can now refer to a clone of the DOM
element from when before the initial animation was called, allowing a
more reliable reverse animation.
Modifier animations

By adding the "to" property to an exit or entrance animation, it will be
executed on that object (valid values are anything you can pass to the
jQuery function). Added the slideTo animation to demonstrate this.
There is now a generic modifier animation

The "animate" animation will animate any CSS property just like you are
used to in jQuery (but it uses transit so its nice CSS3 transitions are
available)
Added slide test

This helps to demonstrate a problem I am having with Firefox and IE
where animations are not starting at exactly the same time