README.md: added warning.

Author: steenzout

README.md

@@ -15,6 +15,8 @@ An [Ansible](http://www.ansible.com) role to setup Oracle Java Development Kit.
 DISCLAIMER: usage of any version of this role implies you have accepted the
 [Oracle Binary Code License Agreement for Java SE](http://www.oracle.com/technetwork/java/javase/terms/license/index.html).
 
+**WARNING**: using `oracle_java_version_update: 121` or above will fail for RedHat (see #34).
+
 
 ## Tests