Updated the README a bit
Updated the README a bit

Includes details about the Android GCM flag.
Clevis/PushNotifications,tomaszhanc/RMSPushNotificationsBundle,nucleartux/RMSPushNotificationsBundle,DABSquared/DABSquaredPushNotificationsBundle,davedevelopment/RMSPushNotificationsBundle,kuldeep199221/RMSPushNotificationsBundle,EDSI-Tech/RMSPushNotificationsBundle,DABSquared/DABSquaredPushNotificationsBundle,richsage/RMSPushNotificationsBundle,DABSquared/DABSquaredPushNotificationsBundle,peternijssen/RMSPushNotificationsBundle,raulfraile/RMSPushNotificationsBundle,funkjedi/PushNotificationPackage