message: docs: add reference to node package
diff: @@ -57,7 +57,7 @@ $ heroku info --app=<tab><tab> # will complete with all the Heroku apps a user h
  # Requirements
  -Only Node 8+ is supported. Node 6 will reach end-of-life April 2019. At that point we will continue to support the current LTS version of node.
  +Only Node 8+ is supported. Node 6 will reach end-of-life April 2019. At that point we will continue to support the current LTS version of node. You can add the [node](https://www.npmjs.com/package/node) package to your CLI to ensure users are on Node 8.
  <!-- install -->
  # Install
  