MAHOUT-1482 Rework quickstart website

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1585027 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1501 ClusterOutputPostProcessorDriver has private default constructor

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1585034 13f79535-47bb-0310-9956-ffa450edef68
MAHOUT-1374 Ability to provide input file with userid, itemid pair

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1585047 13f79535-47bb-0310-9956-ffa450edef68
Merge remote-tracking branch 'remotes/origin/trunk' into trunk