* Add specific test cases for Error Recovery.
* Update hmr/about.js
* Add a test case: should recover after a bad return from the render function
* Add test case: should recover from errors in getInitialProps in client
* Add test case: should recover after an error reported via SSR
* Add a test case: should recover from 404 after a page has been added
* Refactor code base.
* Fix HMR not working issue.
Our hot-reload code on the server has custom webpack error dectection logic.
Is supports only multi-modules entries.
So, we need to all entries as multi-module entries
even if there's just a single entry.
* Add a test case for showing errors over HMR.