Add option to print machine readable output to stdout

When you run bumpversion --verbose, its output gets sent to stderr. This prevents a user to pipe the output into Linux commands like grep without having to redirect stderr to stdout. I don't see a reason why the verbose output should be treated as an error, therefore I'm issuing this pull request.

Furthermore this commit uses False instead of 0 as default value for --verbose, because it's a boolean value and all other options use it too.