title: Cleanup /pipeline folder after docker-push
body: <p>I've created some wercker pipelines with "build" and "docker" pipeline. Both pipelines use different boxes. The "docker" pipeline copies the compiled code from $WERCKER_SOURCE_DIR/target to the correct folders and the last step is a internal/docker-push.
  When I inspect the resulting docker image I still see all the sources in the /pipeline/source folder within the resulting image.</p>
  
  <p>I've tried to do a script step with <code>rm -rf /pipeline</code> after the docker-push, but after inspection the /pipeline (and all sources, build cache, scripts) are still part of the resulting image.</p>
  
  <p>Is there any way to clean this and create a cleaner image (I just want my compiled code in the image).</p>
  
  <p>Thanks,</p>
  
  <p>Danny</p>