v0.6.0

• Fix to chunk regions of subsetted files
• Use cruft to propagate changes from the birdhouse cookiecutter
• Catch documentation build error earlier since doc build is part of regular CI build
• Catch tutorial notebooks out of sync with code earlier since also part of regular CI build
• Use mock imports to facilitate building docs
• Add partial support for xclim v0.21
• Add support for shapefiles in subset_shape