changed version number in ReadMe

Author: JonSnowWhite

README.md

@@ -27,7 +27,7 @@ If you want to use this project as a dependency, you do not have to compile it y
 <dependency>
     <groupId>de.rub.nds</groupId>
     <artifactId>ModifiableVariable</artifactId>
-    <version>3.0.0</version>
+    <version>3.1.0</version>
 </dependency>
 ```