Upgrade to commander 7.0.0

[brandongregoryscott]

commander recently published v7.0.0 which includes a few features that are nice-to-have. Some breaking changes are included but shouldn't be too hard to swap over.

The biggest breaking change will be converting all of the program.option references to use program.opts().option, or destructuring syntax (ie, const { run, watch } = program.opts())

A new configureOutput() function is available for overriding the default stderr/stdout calls, which might be nice to always prefix with our [ERROR] message

I believe there's also support for reusing the same option between a parent and subcommand. Not sure we've needed it so far, but I think I ran into a case where it would be nice to have for the Github command refactor in #124