* Allow for priority to be set on event emitters
* Add payment event emitters
* add new actions/status to checkout state context
* implement event emitters in payment data context
* refactor checkout state context to use new actions in event emitters
* refactor checkout processor to handle new event emitters
* fix type-defs for registered payment methods
* register observer for cheque payment method integration
* add inline todo
* fix sort
* fix tests and add test for priority usage in event emitters
* remove todo and just add explanatory comment
* condense sort logic
* lowercase test description
* abstract emitter callback to reduce code
* don’t process passed in errors if it’s undefined
* improve error response expectation for payment processing event observer
* restructure event-emit directory and convert emitters to promises
- also add emitEventWithAbort function
* implement event emitters as promises
* clean up logic
- return from for loop
- define response as const on each iteration.
- return true if loop completes successfully.
* rename event_emit folder to event-emit
Darren Ethier