Merge pull request #21 from harishreedharan/driver-ha-rdd

Make sure getBlockLocations uses offset and length to find the blocks on...
Merge pull request #22 from harishreedharan/driver-ha-rdd

Shutdown spark context after tests. Formatting/minor fixes
Tweaks testuite to create spark contxt lazily to prevent contxt leaks.
Reorg code that fetches blocks from HDFS