Credits:
--------
low/continents.* and high/continents_med.* are based on gshhsg (http://www.soest.hawaii.edu/pwessel/gshhg/)
released under the GNU Lesser General Public License
The other shapefiles and earth.jpg are copyright Natural Earth and in Public Domain (PD).
See http://www.naturalearthdata.com/about/terms-of-use for details.
