Crashes during server rendering

[gaearon]

reduxjs/redux-devtools@64f58b7#commitcomment-17332926
facebook/react#6689

For now, we should do something like

class AppContainer {
 ...
}

if (typeof window !== 'undefined') {
  AppContainer.prototype.unstable_handleError = ...
}

[calesce]

Closing this since the original React issue was fixed. I've also tested rendering <AppContainer /> on the server and it doesn't crash (even though most people will only need to use it in the client bundle)