build(npm): require node 8 and npm 5
build(npm): require node 8 and npm 5

version updates open the door for using more recent javascript features
as well as leveraging the new package lockfile for more exact versioning

BREAKING CHANGE: drops support for node version 7 and below,
also drops support for npm version 4 and below

ChristianMurphy/nicest,ChristianMurphy/nicest