nugget fails in a Travis CI environment with a memory leak

The progress bar does weird stuff and it causes Travis CI to run out of memory when something else calls nugget while in a coverage check with Instanbul, but only when using async Mocha and calling from within a promise.

Don't ask me why or how.

The solution to stop the leak is to make sure opts.quiet is set i.e. my code now looks like:

    var isInCI = process.env.CI !== undefined
    nugget([link], { dir: tmpDir, quiet: isInCI }, function () {
      isFunction(onDone) && onDone(fullName)
    })

It fails on Linux and OS X images, with all versions of node back to 4.

Start by reproducing the nugget call described in the issue under async Mocha, Istanbul coverage, and Travis CI on the Linux or OS X environments mentioned. Compare behavior with and without opts.quiet; done means the memory leak is addressed without requiring callers to use the workaround, while progress-bar behavior remains correct.