leverage the UNSD GeoArea API for regions

[jmckenna]

• removes use of manually-downloaded UNSD - Methodology.csv file
• instead requests JSON from the UNSD GeoArea endpoint (see tree at https://unstats.un.org/SDGAPI/v1/sdg/GeoArea/Tree )
• the JSON is parsed for country and region names (actually handles region, sub-region, and intermediate regions, but only region and sub-region are returned)

Some sample test results:

• IOC Science and Communication Centre on Harmful Algae, University of Copenhagen - University of Copenhagen, Department of Biology - DK-1353 K\u00f8benhavn K - Denmark

  • returns: ['Europe', 'Northern Europe']

• P. O. BOX LG 99 Legon-Accra, Ghana.

  • returns: ['Africa', 'Sub-Saharan Africa']

fixes #6