We build hadoop 2.0.0-alpha but mahout points to 2.0.0-SNAPSHOT

While looking at the RC bits, I noticed we force some dependencies to be pointed at some SNAPSHOT versions.
Ex: mahout is being pointed at hadoop-2.0.0-SNAPSHOT. But I haven't checked everywhere.

Given that we are working on a release version of Apache Bigtop (incubating) that means the build is not consistently reproducible. And Apache projects have also the habit of deleting their SNAPSHOT artifacts when they move on onto other versions, which would mean that a release of Apache Bigtop (incubating) may not be rebuildable at all in a month or two.