Updating README

JDK 1.7 no longer supported due to auth requirements in core SDK

Author: developersteve

README.md

@@ -11,7 +11,7 @@ Telstra Messaging API
 ## Requirements
 
 Building the API client library requires:
-1. Java 1.7+
+1. Java 1.8+
 2. Maven/Gradle
 
 ## Installation