enable push notification registering in Mixpanel (and potentially other analytics tracker)
send our GCM token to AnalyticsTracker (onRegistered and on app init)
handle mixpanel notification in GCMIntentService
Merge branch 'release/3.0' into issue/1635-mixpanel-push-notifs
fix double notification issue
move registerForCloudMessaging after analytics tracker init
revert auto code styling
clear open activities when tapping a mixpanel notification
Merge pull request #1643 from wordpress-mobile/issue/1635-mixpanel-push-notifs

fix #1635 enable mixpanel push notifications