Port zoom-in and zoom-out functionality from animate.css

Hey! Wanted to add some missing functionality over from the original animate.css for a project. Figured I'd contribute it back in, if wanted.

Adds the following:

[https://github.com/daneden/animate.css/tree/master/source/zooming_entrances](https://github.com/daneden/animate.css/tree/master/source/zooming_entrances)
[https://github.com/daneden/animate.css/tree/master/source/zooming_exits](https://github.com/daneden/animate.css/tree/master/source/zooming_exits)