Check for animation styles on close.

Hello!

We had some problems with vex modals not closing on closeById.
Turns out the problem occured because vex assumes that `$vex` element is styled with an animation.

If it isn't, but the browser supports animations, the animationend event is waited for indefinitely and the modal never actually closed.

I added a check for animation styles on the `$vex` element to fix this and also bumped the Vex version to `2.2.2`.