Have a "scripts/publish.sh" which prepares repo for pushing to pub

[jbdeboer]

The script should:

1. Strip out the build badge so that it does not show up here: https://pub.dartlang.org/packages/angular
2. Strip out tho <a> tags from CHANGELOG.md so that they don't show up in https://pub.dartlang.org/packages/angular chagelog tab.
3. perhaps only have a last change log in the changelog tab on pub.