Add deprecation notice to GCM module README

Jawnnypoo · rogerhu · commit c8718df7fb68 · 2018-04-25T16:16:23.000-07:00
diff --git a/gcm/README.md b/gcm/README.md
@@ -1,6 +1,9 @@
 # Parse SDK Android GCM
 GCM support for Parse Android apps
 
+## Deprecated
+Please note that GCM is deprecated in favor of FCM. This module exists as a backwards compatible solution for projects already using GCM. New apps should instead use FCM.
+
 ## Setup
 
 ### Installation
