Update README.md

Author: JonRowe

README.md

@@ -3,6 +3,8 @@ rspec-mocks is a test-double framework for rspec with support for method stubs,
 fakes, and message expectations on generated test-doubles and real objects
 alike.
 
+**This is the old rspec metagem repository, please see the monorepo rspec/rspec for new issues and releases.**
+
 ## Install
 
     gem install rspec       # for rspec-core, rspec-expectations, rspec-mocks