Update dependencies and build configuration

• Builds using @babel/plugin-transform-runtime and has a dependency on @babel/runtime. This avoids the need to have global regeneratorRuntime defined.

Dev:

• Update testing to latest version of ava.

• Add npm run lint script

Configuration Validity Test

New features:

• Throws custom ConfigurationError if the middleware hasn't been properly set up. #1 (comment)

Initial public release

v1.0.0

Markdown fix