Further details on the testing framework

Signed-off-by: Robert Chu <robert@wibidata.com>
Revisions to setup portion of music tutorial documentation.

* Adjust the Kiji URI used to kiji://.env/kiji_music so user doesn't have to remember ports.
* Remove env var HDFS_ROOT from entire tutorial as it's unneeded if BentoBox or Hadoop+HBase are
installed per tutorial documentation instructions.
* Made definition of KIJI_CLASSPATH simpler.

Signed-off-by: Juliet Hougland <juliet@wibidata.com>
KijiMR UserGuide - Reducers classes overview

Signed-off-by: Milo <milo@wibidata.com>
Removes original, monolithic KijiMR userguide.