deprecate bucky/viz/geoid.py

[mattkinsey]

since we're now outputting the adm mappings at model runtime we should deprecate most of bucky/viz/geoid.py and just read in the mappings from the output directory (see postprocess.py for an example). We will still need to support mapping of fractional populations from counties (for subpopulations spanning multiple counties) but that should be a standalone feature now and will need to be added to the new postprocess.