------------------
- utils.get_crs now leaves EPSG codes instead of converting them to their Proj4
representation.
- Implemented GeometryFileSink that writes ESRI Shapefile, GeoJSON, GML, and
geopackage.
- Added a .to_file() method to all GeometryBlocks.
- Added dry_run parameter (for validation) to .to_file().
- Start using google docstring convention.
- Several minor doc fixes.
- Fix setting of the .crs property in the GeometryFileSource.
- Fixed serialization of raster.Classify.