GIRAPH-704: Specialized message stores (majakabiljo)
GIRAPH-705: Type converters and giraph-hive cleanup (nitay)
GIRAPH-710: Define zookeeper version in a property to allow build time override (apurtell via nitay)
GIRAPH-708: Factories for creation of all IVEM types (nitay)
GIRAPH-709: More flexible Jython script loading (nitay)
GIRAPH-705: Type converters and giraph-hive cleanup (nitay)
GIRAPH-705: Type converters and giraph-hive cleanup (nitay)
GIRAPH-715: Fix MessageValueFactory performance regression (nitay)
GIRAPH-716:  Stop modifying Configuration since it's not thread-safe (majakabiljo)
GIRAPH-718: Output all per-superstep metrics per superstep (majakabiljo)
Merge remote-tracking branch 'upstream/trunk' into GIRAPH-549