This moves development from the original repository:
https://github.com/farr/skyarea

Some minor changes occurred in the course of refactoring:
 * The contents of the module `sky_area.sky_area_clustering` moved
   to `lalinference.kde`.
 * The Python script `run_sky_area` was renamed to
   `lalinference_samples_to_fits` and the command line interface
   was ported from `optparse` to `argparse`.