Allow passing extra args to subscribe in Events::Mixin

[ianks]

For certain pub/sub systems, it's crucial to pass a name or id attribute to each subscriber so they can be individually identified. This ensures correct delivery of a message to a subscription. This PR makes it so the mixin will happily accept optional args and pass them to the adapter. Without this, it would not be possible to correctly implement an adapter for https://github.com/adHawk/hanami-events-cloud_pubsub