* Added test and test data for geo.raster.conversion.raster2polygon(). * Replaced skimage downsampling by GDAL variant. * Removed scikit-image dependency. * Dropped Python 2.7 support due to end-of-life status. * Dropped compatibility module since this was Python 2.7 specific. * Dropped requirements six and packaging. * Added some docs/.rst files to .gitignore. * Updated minimal version of pyproj to 2.5.0.