* Use file hashes instead of BUILD_ID.
Now JSON pages also not prefixed with a hash and
doesn't support immutable caching.
Instead it supports Etag bases caching.
* Remove appUpdated Router Events hook.
Becuase now we don't need it because there's no buildId validation.
* Remove buildId generation.
* Turn off hash checks in the dev mode.
* Update tests.
* Revert "Remove buildId generation."
This reverts commit fdd36a5a0a307becdbd1d85ae3881b3a15b03d26.
* Bring back the buildId validation.
* Handle buildId validation only in production.
* Add BUILD_ID to path again.
* Remove duplicate immutable header.
* Fix tests.
* Reload the page if the buildIds are mismatch.
* Reload the browser with main.js and commons.js buildId mismatch.
* Implement proper reloading with an API to persist the state.
* Add some tests for force reload.
* Change _reload to _forceReload.
* Add a section about reload hooks to the README.
* Allow to add a hook to handle BUILD_ID mismatch.
* Remove readme docs.
* Do not show a custom error to the user.
* Cancel the routing when there's a BUILD_ID mismatch.
* Fix a typo.
* Passing route to SingletonRouter.onBuildIdMismatch
* Handle buildId mismatch automatically.
* Implement a very simple prefetching solution.
* Remove next-prefetcher.
* Require 'whatwg-fetch' only in the client.
* Use xhr in the code.
* Use a simple fetching solution.
* Fix 404 and xhr status issue.
* Move the prefetching implementation to next/router.
* Add deprecated warnning for next/prefetch
* Run only 2 parellel prefetching request at a time.
* Change xhr to jsonPageRes.
* Improve the prefetching logic.
* Add unit tests covering the Router.prefetch()
* Update examples to use the new syntax.
* Update docs.
* Use execOnce() to manage warn printing.
* Remove prefetcher building from the flyfile.js
Because, we no longer use it.
* Move route loading logic to a common place.
* Add router events.
* Add EventEmitter's core API methods.
* Add example app for loading events and docs.
* Fix some typos.
* Get rid of Router.ready()
* Remove events package.
It's already shipping with webpack.
* Handling aborting properly.
* Expose simple attribute based events listener API.
Removed the proposed event listener API from the public API.
* Remove error logged when there's an abort error.
There are many other ways to capture this error.
So, it doesn't look nice to print this always.
* Change router events to pass only the current URL as arguments.
* Add a section about Cancelled Routes to README.
* Immplement the initial singleton Router.
* Use the new SingletonRouter for HMR error handling.
* Use SingletonRouter inside the Link.
* Create an example app using the Router.
* Make the url parameter optional in Router.push and Router.replace
* Add a section about next/router in the README.
