@Override
    public void onTokenRefresh() {
        // Fetch updated Instance ID token.
        Intent intent = new Intent(this, RegistrationIntentService.class);
        startService(intent);
    }
Called if InstanceID token is updated. This may occur if the security of
the previous token had been compromised. This call is initiated by the
InstanceID provider.
app/src/main/java/com/example/android/sunshine/app/gcm/MyInstanceIDListenerService.java