Subcommand suggestions for typos

I'd like for `Commander.Execute` to print a suggestion if the given subcommand looks like a typo similar to what Git does:

```shell
$ git brunch
git: 'brunch' is not a git command. See 'git --help'.

The most similar command is
branch
```

I have a simple implementation of this using https://github.com/agext/levenshtein that I will attach as a PR.