remove react-motion dep

[lipp]

No description provided.

[zemirco]

I've written some pull requests to remove react-motion.

It worked great until the last PR which is dealing with the select component. We simply cannot animate a component which is new to the DOM. We either have to hide it before or decide to get rid of the animation. However hiding it created some issues with keyboard accessibility.

We could use react transition group https://facebook.github.io/react/docs/animation.html instead which would allow us to use CSS animations instead of JS animations like it is now with react-motion.

What do you think?