Merging latest changes from spark main branch

.gitignore

LICENSE

README.md

assembly/README

assembly/lib/PY4J_LICENSE.txt

assembly/lib/PY4J_VERSION.txt

assembly/lib/net/sf/py4j/py4j/0.7/py4j-0.7.jar

assembly/lib/net/sf/py4j/py4j/0.7/py4j-0.7.pom

assembly/lib/net/sf/py4j/py4j/maven-metadata-local.xml

assembly/pom.xml

assembly/src/main/assembly/assembly.xml

bagel/pom.xml

bagel/src/main/scala/org/apache/spark/bagel/Bagel.scala

bagel/src/test/scala/org/apache/spark/bagel/BagelSuite.scala

bin/compute-classpath.cmd

bin/compute-classpath.sh

bin/slaves.sh

bin/spark-daemon.sh

bin/start-master.sh

bin/start-slave.sh