Adding note to README (#8)

DX-164
Adding a note updating the non-supported aspect of the SDK

Author: bradbroge

README.md

@@ -4,6 +4,8 @@
 
 # spreedly-android
 
+Not actively maintained at this time. Contact Support with questions.
+
 # Integration
 All integration options require a Spreedly account and an environment key. See [Create Your API Credentials](https://docs.spreedly.com/basics/credentials/#environment-key) for details.