Update dependencies

This update patches security issues with eslint-utils and lodash.

Update documentation

Nothing serious here - just fixing a typo and adding some clarifying documentation to the README.

Version 3.0.0 release

This major version upgrade changes the way that users will provide their Heroku app's name and configuration. Instead of passing them via NPM command flags, users instead provide that data in a .json_to_heroku_envrc.json file.

lodash has also been updated (via an eslint update) that patches a minor security bug.