Fixed bug with PresenceObserver channel filtering

Certain PNChannels from SubscribeRequest responses with
isPresenceObserver == NO were not passing this filter predicate. Using
the literal NO inside the predicate string fixes this.
Merge pull request #13 from jonathanrauch/master

Fixed weird bug with PresenceObserver channel filtering
Completed Asana tasks:
* #5688796691055
* #5688796691041
* #5688796691045
* #5688796691048
* #5688796691051
* #5688796691003
Merge branch 'master' into asana-5688796691055