Allow react 16 as peerDependency

[okize]

Add prop-types & create-react-class packages to make the minimum amount of changes to be compatible with React 16.

[benbriggs]

👍 thanks! i'm going to follow up with a migration of the example files to 16 as well.

[benbriggs]

I'm going to open up an issue to switch bundled components to ES6 classes so that we don't need the create-react-class dependency long term (even though i prefer the original factory function style 😢 )

[benbriggs]

@okize landed in 1.5.2

[okize]

thanks @benbriggs !!