No more bundled binaries

Changed

• Breaking change: Binaries are no longer bundled in the package. They are downloaded as an npm postinstall task.
• Uses ECMAScript Modules (ESM; es6 modules).
• Zero runtime dependencies.
• Dev: now using @small-tech/esm-tape-runner.
• Dev: now using c8 instead of nyc for coverage.
• Dev: replaced tap-spec and tap-nyc with @small-tech/tap-monkey.