Cannot build demos on react v16

[jaeseok-park]

Hi.

I've tried to build these demos as the readme.md, however they produce many failures as below:

ERROR in ./demos/demo0-simple-transition/index.jsx
Module not found: Error: Cannot resolve module 'react/lib/ReactMount' in D:\Github\react-motion\demos\demo0-simple-transition
 @ ./demos/demo0-simple-transition/index.jsx 1:321-352

To resolve this, I fixed react and react-dom version to v15.5.0. but it seems not to be the best way.
Could you please make this demos buildable on react v16?

Thanks.