SCM information should be validated

The plugin does not currently validate the SCM connection info. When preparing a release with invalid info, the project gets built, the transformed POM is committed, but the branching/tagging is doomed – leaving the user having to perform a rollback.

I would like this plugin to automatically invoke scm:validate:
http://maven.apache.org/scm/maven-scm-plugin/validate-mojo.html

The earlier phase the better for validation. There's no point in compiling the project if the connection strings are wrong.