add support for multiple flow dirrections
Merge remote-tracking branch 'upstream/master' into hydrology
add test case for multiple flow dirrections (incomplete)
Work on ZonalSummarySpec
Change ZonalMin, ZonalMax, ZonalMean to return Int
Merge branch 'master' of github.com:ejc123/geotrellis

Conflicts:
	src/test/scala/geotrellis/raster/op/zonal/TiledPolygonalZonalSummarySpec.scala
Merge remote-tracking branch 'upstream/master' into hydrology
Merge branch 'hydrology' of github.com:Markko/geotrellis into hydrology
finish accumulation test for multiple flow dirrections
Merge branch 'master' into ZonalSummaryFix
Change ZonalMean to return Double
  Make one Mean case class for ZonalMean and ZonalMeanDouble
  Silence success cases in TiledPolygonalZonalSummarySpec
Merge pull request #619 from ejc123/ZonalSummaryFix

Change zonal {min,max,mean} to Int instead of Long
Merge pull request #612 from Markko/hydrology

add support for multiple flow dirrections
Merging upstream changes.