Update READ.ME

Author: ElgarL

README.md

@@ -28,7 +28,7 @@ Then add as a dependency in your pom.xml
         <dependency>
             <groupId>com.github.ElgarL</groupId>
             <artifactId>groupmanager</artifactId>
-            <version>2.9</version>
+            <version>3.1</version>
         </dependency>  
 ```