Allow QueueChanSubscribe

[jirenius]

Issue

It should be optional if a handler uses ChanQueueSubscribe instead of ChanSubscribe.

The queue group should also be configurable, or else resolve to the resource pattern.

Discussion

This feature has been requested and discussed in issue #12

Notes

If ChanQueueSubscribe is used for a resource, mutating events (ChangeEvent, AddEvent, and RemoveEvent) should not be allowed for that resource, as it would cause races with other services belonging to the same queue group.

[jirenius]

Resolved in #80