Advance v3.0.0-alpha.0

• Create new index file. Closes #66.
• Convert reverse from class to function. See #66.
• Convert forward from class to function. See #66.
• Add chicklets and links to README. Closes #69.
• Invoke Proof directly. See #69.
• Update .npmignore and .gitignore. See #69.
• Remove old test helpers. See #69.
• Update LICENSE for 2020. Closes #71.
• Build with only Node.js 12 on Travis CI. Closes #70.
• Build with Actions, ship coverage to Codecov. Closes #67. Closes #68.
• First pass of async/await conversion. See #66.
• Update LICENSE for 2019.

Closes #72.