Update unit test memory to 2 GB
Call commitJob on Hadoop OutputFormats to fix issues with saving on Hadoop 2
Create an empty directory when checkpointing a 0-partition RDD (fixes a
test failure on Hadoop 2.0)
Configure Maven to perform releases
Conform to Sonatype's "Central Sync Requirements"
Include scala version in artifactId
Mark kafka:0.7.2-spark as an externally provided dependency
Release v0.7.1
Update development version to 0.7.2-SNAPSHOT
Spark-742: TaskMetrics should not employ per-record timing.

This commit merges together all the changes for purpose of cherry-picking
Merge pull request #588 from pwendell/branch-0.7

Spark-742: TaskMetrics should not employ per-record timing.
Merge remote-tracking branch 'origin/branch-0.7' into branch-0.7