Added puma-mapping.csv, a table that lists each PUMA and all meaningfully
adjacent PUMAs.  I say 'meaningfully adjacent' because if Long Island Sound
separates two PUMAs - one in the Bronx, one in Queens - those PUMAs are not
contiguous for the purposes of food distribution.

Modified agency_targeting.py to allocate food for regions for which there
are no agencies.  Also made minor cleanups.