Moved SEPP trigger density calculation to its own function for easier testing.  TODO: now have a list of tests to implement, do so.
Added new table for Chicago divisions, since it made no sense to keep these in the Division table, whose SRS was designed for London ONLY.
Added to populate method to add Chicago data.
Started working on a series of functions (or class?) to extract OSM data from a table.
NB table is created by dumping OSM data using osm2pgsql command.
Migration.