Framework integrations

Hi,

can you share your thoughts where should framework specific stuff be placed. For example I have to integrate following:
- GCM (push notifications) - regular push notifications with news
- Google Analytics - tracking for pageview's and events

Where should GCM code reside (`InstanceIDListenerService` and `GcmListenerService`)? How would you handle processing of incoming notifications/payload.

Where would you place tracking related classes and should we call tracker from presenter or usecase?