Force the jar plugin into our classpath in the example

examples/word-count/build.gradle

@@ -11,6 +11,7 @@ buildscript {
          * use if you want to use this build.gradle outside of gradleTest
          */
         classpath 'com.github.jruby-gradle:jruby-gradle-storm-plugin:%%VERSION%%'
+        classpath 'com.github.jruby-gradle:jruby-gradle-jar-plugin:1.0.4+'
     }
 }