v4.0.0

Breaking

• Require Node.js 10 bbc3121
• Return undefined instead of null when no match b1cd76b

Breaking for TypeScript users

• Only use a CommonJS export for the TypeScript definition
  You need to change import yn from 'yn'; to import yn = require('yn');

Enhancements

• Support on and off words 65e8faf

v3.1.1...v4.0.0