In engines, it states that this module supports Node.js 4.x. I wonder out loud if it's worth ripping off that band aid :) I think this is a great read on the topic:
https://medium.com/@mikeal/stop-supporting-old-releases-70cfa0e04b0c

For many of our modules, we're dropping support for 6 as soon as possible, as may of our own dependencies are starting to drop support. I'm a little surprised this hasn't gotten y'all in trouble yet with the upgrade of devDependencies :)