[SPARK-7579] [ML] [DOC] User guide update for OneHotEncoder
[SPARK-7579] [ML] [DOC] User guide update for OneHotEncoder

Author: Sandy Ryza <sandy@cloudera.com>

Closes #6126 from sryza/sandy-spark-7579 and squashes the following commits:

5af803d [Sandy Ryza] SPARK-7579 [MLLIB] User guide update for OneHotEncoder

(cherry picked from commit 829f1d95bac9153e7b646fbc0d55566ecf896200)
Signed-off-by: Joseph K. Bradley <461476587780aa9fa5611ea6dc3912c146a91760@databricks.com>

andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap,andrewor14/iolap