namespace for handling GTFS to Datascript convertion and vice versa.

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.

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

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 using java references
... just data