MAHOUT-1616 Better support for hadoop dependencies. Now Apache Mahout's default hadoop version is 2.2.0, and we handle hadoop dependencies via hadoop-client artifact. This closes apache/mahout#54
MAHOUT-1611: Preconditions.checkArgument in org.apache.mahout.utils.ConcatenateVectorsJob
MAHOUT-1611 reverted to using Hadoop 1.x APIs, closes apache/Mahout#63