SPARK-1929 DAGScheduler suspended by local task OOM

DAGScheduler does not handle local task OOM properly, and will wait for the job result forever.

Author: Zhen Peng <zhenpeng01@baidu.com>

Closes #883 from zhpengg/bugfix-dag-scheduler-oom and squashes the following commits:

76f7eda [Zhen Peng] remove redundant memory allocations
aa63161 [Zhen Peng] SPARK-1929 DAGScheduler suspended by local task OOM
Fixed the error message for OutOfMemoryError in DAGScheduler.
Updated dev Python scripts to make them PEP8 compliant.

Author: Reynold Xin <rxin@apache.org>

Closes #875 from rxin/pep8-dev-scripts and squashes the following commits:

04b084f [Reynold Xin] Made dev Python scripts PEP8 compliant.
SPARK-1933: Throw a more meaningful exception when a directory is passed to addJar/addFile.

https://issues.apache.org/jira/browse/SPARK-1933

Author: Reynold Xin <rxin@apache.org>

Closes #888 from rxin/addfile and squashes the following commits:

8c402a3 [Reynold Xin] Updated comment.
ff6c162 [Reynold Xin] SPARK-1933: Throw a more meaningful exception when a directory is passed to addJar/addFile.