Pushing a new version

When pushing a new version:

• run grind update-gh-pages
• rev the version in the pubspec.yaml file
• rev the corresponding version in lib/src/cli_app.dart
• make sure the changelog.md file is up-to-date
• create a tag git tag vX.Y.Z where x.y.z is the release number
• push the tag git push origin vX.Y.Z
• commit
• create a new github release (https://github.com/google/stagehand/releases)
• push to pub
• update the stagehand.io docs (grind update-gh-pages)
• possibly, rev the version to the next highest number, with the -dev suffix