GIRAPH-696: Should be able to spill giraph metrics to a specified directory on HDFS
GIRAPH-697: Clean up message stores (majakabiljo)
GIRAPH-693: Giraph-Hive check user code as soon as possible (nitay)
GIRAPH-688: Make sure Giraph builds against all compatible YARN-enabled Hadoop versions, warns if none set, works w/new 1.1.0 line (ereisman)
GIRAPH-311:  Master halting in superstep 0 is ignored by workers (majakabiljo)
GIRAPH-698: Expose Computation to a user (aching)
GIRAPH-676: A short tutorial on getting started with Giraph
Merge remote-tracking branch 'upstream/trunk' into GIRAPH-623