* Remove hoist-non-react-statics from with-router

* Drop hoist-non-react-statics from package.json

* Revert #6030

* Fix _app childContextTypes

Fixes parts of #5716. I had some issues with the test suite but I'm fairly certain that I got it working correctly.

* Make sure const/async is transpiled

* Use babel common compilation instead

- Replaces taskr-babel with taskr-typescript for the `next` package
- Makes sure Node 8+ is used, no unneeded transpilation
- Compile Next.js client side files through babel the same way pages are
- Compile Next.js client side files to esmodules, not commonjs, so that tree shaking works.
- Move error-debug.js out of next-server as it's only used/require in development
- Drop ansi-html as dependency from next-server
- Make next/link esmodule (for tree-shaking)
- Make next/router esmodule (for tree-shaking)
- add typescript compilation to next-server
- Remove last remains of Flow
- Move hoist-non-react-statics to next, out of next-server
- Move htmlescape to next, out of next-server
- Remove runtime-corejs2 from next-server

- Implements Lerna
- Moves all source code into `packages/next`
- Keeps integration tests in the root directory

* Add withRoute HOC

Rebased (squashed)
- removed routerToProps
- updated hoist-non-react-statics
- improved propTypes

* Expose the whole Router instead of the route.

* Make the example simple.

* Update examples and the readme.

* Add a test case.