* refactor collector worker
* use Promises to resolve the async request and push result at once
* use addEventListener for request events (load, err, …)
* move methods to sort out approved comments and commits into worker because of the better performance
* set fetch interval to 5min (300000ms)
* move methods to sort approved commits/comment to worker
* extend API to add one url at some time
* fetch comments before render charts
* code formatting
* process comment data for review chart