Complete rewrite

[nkbt]

• Remove react-motion dependency
• Switch to iframe resize sensor
• All animations are done with css at this point. Most likely I will find the way to leave it to the end user with some sane defaults.

More updates will be added later to preserve as much backward compatibility as possible

Will be release as 5.0 at some point when good enough.

Most examples work out of box. Except some that rely on removed features like onRest/onMeasure callbacks, etc. They will be added later.