Merge pull request #575 from mridulm/master

Manual merge of yarn branch to trunk
Add back line removed during YARN merge
Update unit test memory to 2 GB
Create an empty directory when checkpointing a 0-partition RDD (fixes a
test failure on Hadoop 2.0)
SPARK-739 Have quickstart standlone job use README
Merge pull request #580 from pwendell/quickstart

SPARK-739 Have quickstart standlone job use README
Exclude old versions of Netty, which had a different Maven organization
Merge branch 'master' of github.com:mesos/spark
Attempt to fix streaming test failures after yarn branch merge