title: npm package.json OS specific dependency
body: <p>Is there a way to specify OS specific dependencies in a npm package.json file?</p>
  
  <p>For example, I would only want to install 'dbus' (<a href="https://npmjs.org/package/dbus">https://npmjs.org/package/dbus</a>) as a dependency for my module if the user is running Linux. I would have a different dependency for Mac and Windows.</p>