Publish checklist

• Check that the README.md is up to date (Current development status requires Dart SDK build 29720 (0.8.9))
• Check that the CHANGELOG.md is up to date
• Remove -pre suffix from version in pubspec.yaml
• Complete Commit checklist
• run pub publish to check if it shows any warnings
  • fix the issues
• add a tag with the new release number (git tag x.x.x, git push --tags)
  • remove pushed tags (git tag -d x.x.x, git push origin :refs/tags/x.x.x)
• pub publish
• increment version in pubspec.yaml and add -dev suffix
  • commit pubspec.yaml updates
• check all open issues are still relevant
• move all open issues from milestone current to next
• rename milestones
  • current to x.x.x (published package version) and close the milestone
  • next to current
• create new milestone next