Merge pull request #451 from Qiuzhuang/master

Fixed Window spark shell launch script error.

 JIRA SPARK-1029:https://spark-project.atlassian.net/browse/SPARK-1029
(cherry picked from commit d749d472b37448edb322bc7208a3db925c9a4fc2)

Signed-off-by: Patrick Wendell <pwendell@gmail.com>