JavaScript API Changes

Here are some things we want to add or change to the JavaScript API.

`animateIn` and `animateOut` would be renamed `transitionIn` and `transitionOut`, to make it less confusing that a function called "animate" only works with transitions.

Right now there's no method to add animations, because all you need to do is add a class. But we could write a wrapper that also handles removing the class for you, and giving you a callback that fires when the animation completes (if it has a finite number of loops).

It might look like this:

``` js
MotionUI.animate('#element', 'wiggle', function() {
// Animation done
});
```