Set version back to 2.1-SNAPSNOT
Set version back to 2.1-SNAPSNOT

This reverts commit 470383eac921bdc7e37be464d4abf3bd96c2931b.

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