Release Mvcc version 2.0.0-alpha.0.

[bigeasy]

• Update README.md. Closes #45.
• Build with Actions, ship coverage to Codecov. Closes #43. Closes #44.
• Add .npmignore. See #45.
• Update .gitignore. See #45.
• Use this for any constants or common utilities. Closes #52.
• Upgrade homogenize to 2.0.0-alpha.0. Closes #51.
• Upgrade advance to 3.0.0-alpha.0. Closes #49.
• Upgrade riffle to 2.0.0-alpha.1. Closes #48.
• Run Istanbul at Travis CI. See #45.
• Remove old test directory. See #45.
• Upgrade dilute to 2.0.0-alpha.0. Closes #47.
• Upgrade twiddle to 2.0.0-alpha.0. Closes #46.
• Convert README.md to Markdown. See #45.
• Update Proof to 9.0.2. See #45.
• Build with only Node.js 12 on Travis CI. Closes #42.
• Update LICENSE for 2020. Closes #41.
• Build with Node.js 8 on Travis CI.
• Do not build with Node.js 5 on Travis CI.
• Upgrade proof to 3.0.x.
• Use Proof Redux.
• Upgrade Proof to 1.2.x.
• Update LICENSE for 2017.
• Plain text README.
• Further indent.
• Remove test sub-directory.
• Tidy package.json.
• Build with latest Node.js 6 on Travis CI.
• Pin dependencies to minor version.
• Indent package.json.