title: java.lang.NoClassDefFoundError: org/apache/tools/ant/util/ReaderInputStream vaadin+gradle+intelliJ
body: <p>I have been working fine with <code>Vaadin + Gradle + IntelliJ</code> until yesterday night when I introduced SLF4J(logback) logging to my application. Since then I can't make my project anymore due to <code>classDefFoundError</code> of <code>org/apache/tools/ant/util/ReaderInputStream</code>.</p>
  
  <p>I can't link it with any transitive dependency of any contained jar in application, but even if I remove <code>SLF4J</code> libraries I still can't make my application, so I am wondering what changed? </p>
  
  <p>I am using <code>vaadin gradle plugin 0.9.5</code> and <code>gradle 2.2.1</code>. Has anyone ever encountered this problem? I was reading another post where someone had the same issue, but the solution he proposed is not valid to my application. He proposed to comment some of the lines in <code>vaadin.gradle</code>, which my application doesn't have.</p>