doc: standardize references to node.js in docs

trivial commit to fix a couple inconsistent references to
the name of the project

PR-URL: https://github.com/nodejs/node/pull/4136


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Roman Klauke <romaaan.git@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>