Updated documentation to refer to correct configuration required to use geb-saucelabs

We made the following changes to the sample build.gradle listed on http://www.gebish.org/manual/0.9.2/build-integrations.html

- include the project-report plugin 
- remove the tasks closure
- include a tasks.withType(Test) closure which sets the destination directories

See http://stackoverflow.com/questions/22602959/gradle-geb-saucelabs-plugin/22759012#22759012 for further information