Update `EventEmitter2` to `v4`
Update `EventEmitter2` to `v4`

Ref: https://github.com/asyncly/EventEmitter2/blob/4a2549895ff201d6c917d97165c3f1a690afd84c/CHANGELOG.md#411---2017-03-29

sonarwhal/sonar,alrra/sonar,sonarwhal/sonar,sonarwhal/sonar,alrra/sonar,alrra/sonar