v4.0.0

Breaking:

• Require Node.js 8 2e99867
• Rename box style single-double to singleDouble
• Rename box style double-single to doubleSingle

Breaking for TypeScript users:

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

Enhancements:

• Add bold box style
• Upgrade dependencies 2e99867

v3.2.0...v4.0.0