FEATURE: check node version before running

[inigomarquinez]

Detailed Description

It would be good to check if the user is running the package with an allowed nodejs version and throw an error message otherwise.

Context

As the license-checker could start using node features not supported by old node version, it's important for the user to know if they can run it or not with their current node version.

Possible Implementation

Using this package: https://www.npmjs.com/package/please-upgrade-node

Example of a library using it: https://github.com/typicode/json-server/blob/master/src/cli/bin.js