Chore: bring tooling up to speed and release a new version

[erezrokah]

This is long overdue (see #237)

We need to:

1. Update dependencies (probably drop node 8 support).
2. Add linter + formatter + CI
3. Release a major version

[erezrokah]

Closed via https://github.com/netlify/netlify-lambda/releases/tag/v2.0.0