Update README to latest EmberFire version
Update README to latest EmberFire version

FirebaseExtended/emberfire,IsaiahJTurner/emberfire,rtablada/emberfire,MattMSumner/emberfire,IsaiahJTurner/emberfire,FirebaseExtended/emberfire,FirebaseExtended/emberfire,FirebaseExtended/emberfire,MattMSumner/emberfire,rtablada/emberfire,leifcr/emberfire,leifcr/emberfire