isMounted is an anti-pattern [0], is not available when using ES6
classes, and is on its way to being officially deprecated.
eslint-plugin-react recently added the react/no-is-mounted rule in
3.12.0 that prevents its use.
[0]: https://facebook.github.io/react/blog/2015/12/16/ismounted-antipattern.html
Finishes #633
When there are static variables like `propTypes` and `defaultProps`, we shouldn't export them until we have actually set them onto the `Component`. This may change if the current ES7 proposal for static class properties gets accepts, and we update to support it.
By exporting `propTypes` as a named export *as well* as attaching them to the "class", they can be explicitly imported by tests and other components in a way that aligns with the future ES6 module dependency graph, rather than as an arbitrary property that isn't statically verifiable. Doing both is great imo.
Thoughts?
