React 15 Update

• Updated to React 15
• Proptypes as standalone package
• Moved React stuff to peer dependencies (react motion now the only dependency)

Don't forget, due to the Peer Dependencies, you'll need to install your own version of React if you want to fork and run this locally. I'd suggest using 15.4.4 for React/React Dom for now.

So, npm install react@^15.5.4 react-dom@^15.5.4 without the --save and you should be good to go.