v4.0.0

Dependency Update and Bug Fixes

• QueueService.js:
  • Fixed using async w/ promise executors
  • Fixed publishMessage possibly calling back twice
• BatchQueueWorker.js: Fixed not waiting for messages to get acked before doing the next one
• tests:
  • Fixed using async w/ promise executors
  • disabled why-is-node-running for now
• .eslintrc.json: Updated linting definitions
• .gitignore: Allow package-lock.json
• package.json: Updated all dependencies to latest, bumped to 4.0.0
• .travis.yml: Always test node v12