Optional flag to not run using docker

[jebentier]

The shear details that come from this summary generation is incredible. I'd love to be able to use this. We're running in an environment that has access to ruby, but not to docker though. I was curious if you would be open to an optional argument to the plugin that would execute the formatter directly rather than using docker run? I'd be more than happy to make the PR for this feature as well.