geotrellis/geotrellis — pull request #621 by lossyrob (2013-11-07 01:11:38+00:00)
Title: 	Zonal operations for DataSource refactor

- Note raster-based zonal operations use .global, so the raster will converge.
- Moved combine and combineOp to DataSourceLike.
- Removed ZonalClassification. In going over the algorithm I realized I implemented incorrectly, and I'm not entirely clear what the correct implementation is.