Async awaitify code

[DavidWells]

Was going through the course again and refactored co library out of most of the code in favor of async await.

Totally up to you if you want to merge 😃

The only thing I didn't touch was the tests.

Also fixed 2 missing correlationIds imports in:

• https://github.com/theburningmonk/manning-aws-lambda-in-motion/blob/5708e85765a84f276168595986270455a618043d/functions/accept-order.js#L19
• https://github.com/theburningmonk/manning-aws-lambda-in-motion/blob/5708e85765a84f276168595986270455a618043d/functions/fulfill-order.js#L19

Thanks for this awesome course

The middy wrapper pattern is super nice https://github.com/theburningmonk/manning-aws-lambda-in-motion/blob/master/middleware/wrapper.js