adding MapReduce functionality to GraphComputer.
removed the concept of a TraversalEngine. The long slog ahead.
the slog continues.... XXXComputerSteps implemented for SideEffects with respective MapReduce implementations .... now comes making this work for Giraph. Oh lord.
wow. I can't believe I got the MapReduce abstraction to work over Giraph.... its all downhill from here. cleanup, organizing, and a few API tidbits to settle here and there.
got MapReduce working for both Giraph and TinkerGraph. Score.
merging in new MapReduce framework. Still need to tweak but the body is solid and tests pass.