v3.0.0

[3.0.0] - 2019-02-13

Changed

• sets a new peer dependency to be at least React 16.8
• converts component to functional component and uses the useCallback
  hook for the
  handleKeyDown event memoization
• wraps the component and forwarded ref higher-order component in
  React.memo
• updates example to use useState
  and useCallback
  to toggle the button states (text and background color, where applicable)
• rewrites the tests in
  react-testing-library
  to focus less on internals and more on what an end-user might see (and really
  to try it out, too)