Removed an unnecessary byte array in the middle. Probabaly will have to bring it back if we do block level data movement.

Enabling/disabling HTTP pipelining is a config option now. Performance tradeoffs are not obvious yet.

- Added GroupByTest.scala for benchmarking.

phase of DfsShuffle.

Fixed a small bug in DFS shuffle -- the number of reduce tasks was not being set based on numOutputSplits

well as versions of the shuffle operations that set the number of splits
automatically.

don't all hit the same nodes at the same time.

These tasks were being subjected to delay scheduling but then counted as
having been launched on a preferred node. The solution is to have a
separate queue for them and treat them as preferred during scheduling.

Conflicts:
	src/scala/spark/SparkContext.scala

Using the latest one from Matei.

are used to create an initial copy of each config file if the user does
not have one. This way, users won't accidentally commit their changes to
config files to git.

use this. Closes #12.