namespace for parsing a GTFS feed into a Datascript transaction.

The algorithms coerces GTFS csv files into entities that reference
each other through IDs. The IDs are taken directly from GTFS.

A small dynamic renaming is performed to make it more compatible
with Datascript design. The renaming is based on the GTFS naming
convention, for example: stop_lon, stop_url, trip_id, trip_headsign, etc.

We transform those strings into: :stop/lon, :stop/url, :trip/id,
:trip/headsign.

This is important to be able to create relationships between entities through
transactions, for example {:trip/id 1, :trip/route [:route/id 1]}. This
allows us to create relationships between entities without actually having
them, i.e. thread them simply as data