Salvage milesj 2.0 branch

[hongaar]

See what we can salvage from the 2.0 branch by @milesj.

https://github.com/dthree/vorpal/pull/272/files

Seems there are some useful changes in there, from the added CHANGELOG.md in that branch:

2.0.0 [IN PROGRESS]

💥 Breaking

• Updated minimum Node.js requirement to v6.10 (oldest LTS).
• Updated Inquirer.js to v3.1 from v0.11.
• Removed Command#autocompletion method.
• Renamed Command#helpInformation to Command#renderHelp.

🚀 New

• Added Vorpal#title, Vorpal#version, Vorpal#description, and Vorpal#banner descriptor methods.
  • Renders in the header of help and menu screens.
• Added a new options object as the 3rd argument to Vorpal#command.
  • Supports a new default option.
  • Supports the old autocomplete functionality as a fallback.
• Added a new vorpal_exit event.

🐞 Fixed

• Will now properly exit all scenarios if Ctrl + C is pressed.
• Now supports slashes in autocomplete list values.
• Improvements to variadic argument parsing.

🛠 Internal

• Migrated to 100% ES2015 syntax.
• Migrated to Yarn from NPM.
• Migrated to Yarn scripts from Gulp.
• Updated to no longer require or build with Babel.
• Updated to the latest ESLint (based off Airbnb config).
• Removed the dist folder from the repository.