Examples of generating maps

[rabdill]

For mapping, it seems worthwhile to encourage combining the compendium data with the rnaturalearth package. We already have the code for mapping compendium countries from the first paper; it would be helpful if we made it easier for people. From Benjamín:

I think I was looking for the file (if any) you used to map the countries in the HMC metadata to the world map data that comes with rnaturalearth. In the end, I was able to reproduce the HMC map by regrouping subregions in rnaturalearth metadata to match the 7 major regions you used.