Add `--verbose` flag

[sermuns]

Great tool, just what I was looking for.

When running a heavy command, it would be nice to be able to see the progress. I think it makes sense to add --verbose flag which make it possible to see stdout/stderr of the command being ran.

What do you think? I could take a look at a PR if you're interested.

[terror]

Thanks!

For sure, I suppose we can show intermediate steps like what commands we've ran, what the output is, etc. Feel free to have a crack at it.