MAHOUT-1561, MAHOUT-1568, MAHOUT-1569 text-delimited Spark readers and writers with drivers and a CLI for 'spark-itemsimilarity' closes apache/mahout#22
disabled ItemSimilarity test until we can work out how to run them without MAHOUT_HOME and SPARK_HOME being set
MAHOUT-1541, MAHOUT-1568, MAHOUT-1569 fixed a build test problem, drivers have an option new to not search for MAHOUT_HOME and SPARK_HOME
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/mahout
MAHOUT-1541 backed out compatability with legacy Item Similarity, now outputs raw LLR scores
MAHOUT-1541, MAHOUT-1568, added option to ItemSimilarityDriver to allow output that is directly search engine indexable, also some default schema's for input and output of TDF tuples and DRMs
MAHOUT-1583: cbind() operator for Scala DRMs
This closes apache/mahout#20

Squashed commit of the following:

commit 1baf3fcebf2cd49eb6487afe4eaed689653a3562
Merge: 41f0671 9bfb767
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 12:32:34 2014 -0700

    Merge branch 'master' into MAHOUT-1583

commit 41f0671c9ccca81883475437fe18056563c1f8ac
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 12:27:26 2014 -0700

    Adding assignment time comparison test

commit 6e115c87639ffb111b2e089d7ecdf0eaeecbb02b
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 16 18:42:42 2014 -0700

    + Licenses.

commit d3e905b5a92735822efe717f8b7a57c80bc56478
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jun 16 18:09:59 2014 -0700

    initial writeup
MAHOUT-1529: third collection of various edits against private branch

Squashed commit of the following:

commit 4328aae135bc56c02b944c21af2cfd6629b262bf
Author: Dmitriy Lyubimov <dlyubimov@apache.org>
Date:   Mon Jul 7 13:13:26 2014 -0700

    Various 1529-related stuff collected from private fork