Multi logging WIP

[bbugh]

Note: The multi_test.rb in the root folder is there to do quick tests if you want to use it.

Describe the change

Adds logging to ProgressBar::Multi.

Why are we doing this?

There have been many times where I've wanted a multi progress bar that also outputs text - tests, async scripts, ETL, etc.

Benefits

You can use it in more places where you need logging and progress.

Drawbacks

Not sure of any drawbacks.

Requirements

None of these yet, but will if it works

• [ ] Tests written & passing locally?
• [ ] Code style checked?
  • Rubocop seems to be out of date - many unrelated formatting issues
• [ ] Rebased with master branch?
• [ ] Documentation updated?
• [ ] Changelog updated?

Closes #51