README.md: update maven coordinates to version 2.5 (closes apache#26)

Author: PascalSchumacher

README.md

@@ -63,7 +63,7 @@ Alternatively you can pull it from the central Maven repositories:
 <dependency>
   <groupId>commons-io</groupId>
   <artifactId>commons-io</artifactId>
-  <version>2.4</version>
+  <version>2.5</version>
 </dependency>
 ```