Re-enable openjdk6 builds (#362)
Re-enable openjdk6 builds (#362)

chrysalag/lenskit,linjunleo/lenskit,tajinder-txstate/lenskit,kluver/lenskit,amaliujia/lenskit,vaibhav345/lenskit,tajinder-txstate/lenskit,tajinder-txstate/lenskit,kluver/lenskit,amaliujia/lenskit,chrysalag/lenskit,vaibhav345/lenskit,kluver/lenskit,binweiwu/lenskit,aglne/lenskit,tajinder-txstate/lenskit,kluver/lenskit,blankazucenalg/lenskit,aglne/lenskit,martinlaz/lenskit,blankazucenalg/lenskit,vaibhav345/lenskit,martinlaz/lenskit,vijayvani/Lenskit,vijayvani/Lenskit,kluver/lenskit,binweiwu/lenskit,vaibhav345/lenskit,linjunleo/lenskit