2.0.0

• Update to Firebase Cloud Message
• Update Google Play Service Base to 9.0.2
• Remove RxGcmService

1.1.0

• Update Google Play Service to 9.0.0
• Use fromCallable to register/remove token instead of create Observable

1.0.1

• Verify whether Google Play Service is installed / update
• Verify whether Subscribers isUnsubscribed and clean after use

1.0.0

Update README.md