Changed Spark version back to 0.6.0.
Use current directory for unit test warehouse directory so we can run on
machines without root (need to create /user/hive/warehouse).

Also removed the memory reporting code and will put them back in when
the corresponding change is merged into Spark.
Only initialize SharkEnv once for unit tests.
Fixed commit path from the previous cherry pick.
Fixed SharkEnv.sc == null problem.
SHARK-81 #resolve Don't use null bitmaps to track NULLs in uncompressed
string columns.
Wrap classloader for ant.
Merge pull request #74 from dennybritz/antfix-master

Wrap classloader for ant.
Change Spark version to 0.7.0-SNAPSHOT
Updates based on Spark shuffle refractoring.
Add table property and conf var for RDD storage level.
Merge pull request #76 from harveyfeng/master-storagelvl

Add table property and conf var for RDD storage level.
Initial cut for Shark-64
Update README.md
Move Shark's CoGroupedRDD from spark.rdd to spark package, to avoid conflict.
Merge remote-tracking branch 'src/master' into master-updates
Set default cache storage level to MEMORY_AND_DISK
Force handler threads to wait for RDD caching to complete before serving requests
cleanup
Make sure to pass  SCALA_HOME and MESOS_NATIVE_LIBRARY
to executors, and SPARK_HOME to SparkContext