RE: https://github.com/zeit/next.js/issues/4587, this pull request improves the with-segment example.
Previously, only SSR page loads were tracked. This pull request adds manual page view logging via `Router.events.on('routeChangeComplete')` in `Page.js`.
There is also a minor bug fix on the textarea to remove a console error.
I wrote a [script](https://github.com/j0lv3r4/dependency-version-updater) to update dependencies recursively in `package.json` files, e.g.:
```
$ node index.js --path="./examples" --dependencies="react=^16.7.0,react-dom=^16.7.0"
```
This PR contains the result against the examples folder.
* Examples: clarify language around Yarn create & npx
* add missing READMEs and create-next-app usage
* suggest people tag jthegedus in firebase related issues
* add yarn alt instructions
* cerebraljs example readme & fixes
