Add geom_map geometry for plotting geographic maps about plotnine

[has2k1]

I am working on a mapping geom (geom_carto), with geopandas and cartopy. Using cartopy as the backend though feature rich (real cartographic projections), is not straight-forward and there are changes I would want in cartopy.

I hoped to have it for the next minor release, though if I cannot tame cartopy in time, I may in the meanwhile create an alternative projection-less mapping geom just like geom_map.

[liuzongquan]

plotnine is so great! thanks to @has2k1 ~

[jmccreight]

+1

[cwerner]

Hi. New user here. Very excited about this project.

Is there any update on the geom_carto feature @has2k1 ? Also, is there any interest in also supporting gridded geodata (I'm thinking xarray: https://github.com/pydata/xarray)? I think this would be an awesome match!

[has2k1]

@cwerner

geom_carto depends on cartopy acquiring a standard way to add artists, e.g. GeomCollection as suggested.

I have not looked into xarray, so my imagination on how to use it as a datasource it is blank.