v2.0.0-beta.0

Major update with great improvements in usability, with support for modern
language features such as class and async/await. Now also uses
@fanoutio/pubcontrol@2.

Added

• Added ESM build. Uses Rollup (https://rollupjs.org/) to build bundles for consumption as
  CommonJS, ESM, and the Browser.
• Added new simple NodeJS based demo, providing a server and a publisher, designed
  to be used with pushpin (https://pushpin.org).
• Added a shimmed Buffer object to browser build, as it is needed during JWT authorization.
• IDE metadata for IntelliJ IDEA.

Changed

• Repository now called js-grip to reflect that this is useful in all types of JavaScript,
  including the browser.
• Now distributed as a public scoped package @fanouio/grip.
• Source files and tests rewritten in modern style JavaScript
• Source files moved from /lib to /src
• Basic data structures now using ES6 classes.
• Start using "changelog" over "change log" since it's the common usage.
• Bump major version to 2 to indicate that this is a modernized new version.
• Improved README by being more straightforward with the basic use case.
• GripPubControl now directory inherits from PubControl.
• GripPubControl.publish API has been changed, and the callback is now optional.
  If no callback is provided, a Promise is returned instead.

Removed