title: Sauce Labs upload files with nightwatch.js
body: <p>I have tests written with nightwatchJs that are run with remote sauce labs selenium (aka ondemand.saucelabs.com).
  In the tests flow, I need to upload a local file.
  When I run tests locally, I use <code>setValue</code> method. But this approach does not seem to be a good one with sauce labs.
  Is there a proper way to upload local files with nightwatch and sauce labs?</p>