MAHOUT-1451 Cleaning up the examples for clustering on the website

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1577126 13f79535-47bb-0310-9956-ffa450edef68
Updated CHANGELOG for fixed JIRA tickets.

git-svn-id: https://svn.apache.org/repos/asf/mahout/trunk@1577293 13f79535-47bb-0310-9956-ffa450edef68