Support React 16 (#496)

• New flow definitions, fixes children typing

Breaking

• Dropping support for older React. Currently supported versions are ^0.14.9 || ^15.3.0

Changes

• Upgraded all React components to use ES6 classes
• Replace React.PropTypes with prop-types package

PRs:

• #463 @MichaelDeBoey Use 'react-dom/test-utils' package instead of 'react-addons-test-utils'
• #462 @MichaelDeBoey Update deprecated 'create-react-class' depende...

• externalize stripStyle #452 by @bearcott
• Migrated deprecated React.PropTypes and React.createClass #446 by @Andarist
• Fix link to TypeScript types #443 by @pshrmn
• Refactored demo and fixed flow check errors #435 by @therewillbecode
• Fix broken link #430 by @codler
• Unmounted component setState fix #420 by @alleycat-at-git