Misc typo fixes
Refactor output() method to simplify and accommodate other types
Adjust ALS output method too
Issue #59 : add popularRepresentativeItems() method as an experiment
Issue #72 : avoid NPE during RDF regression /classify
Typo fixes
Add a better error on bad column
Manually chop up huge ID sets in output to avoid OOM issues downstream in Crunch/Avro
Merge remote-tracking branch 'remotes/origin/master' into MR1