[SPARK-4312] bash doesn't have "die"

sbt-launch-lib.bash includes `die` command but it's not valid command for Linux, MacOS X or Windows.

Closes #2898

Author: Jey Kottalam <jey@kottalam.net>

Closes #3182 from sarutak/SPARK-4312 and squashes the following commits:

24c6677 [Jey Kottalam] bash doesn't have "die"

(cherry picked from commit c5db8e2c07e442654f3d368608108e714e080184)
Signed-off-by: Patrick Wendell <pwendell@gmail.com>
SPARK-4230. Doc for spark.default.parallelism is incorrect

Author: Sandy Ryza <sandy@cloudera.com>

Closes #3107 from sryza/sandy-spark-4230 and squashes the following commits:

37a1d19 [Sandy Ryza] Clear up a couple things
34d53de [Sandy Ryza] SPARK-4230. Doc for spark.default.parallelism is incorrect

(cherry picked from commit c6f4e704214097f17d2d6abfbfef4bb208e4339f)
Signed-off-by: Patrick Wendell <pwendell@gmail.com>