Support React 17

React 17 adds support for async rendering which will need some testing and tweaking to properly support.

It explicitly removes support for various lifecycle methods on class components:

componentWillReceiveProps
componentWillMount
componentWillUpdate

and moves to use the new ones

getDerivedStateFromProps
getSnapshotBeforeUpdate

These new methods, and the deprecation warnings were added back in 16.3.

Do do have a couple places that I believe are still using the old methods, although there was a pass to remove them.