Fixes #34 - exportgtfs with non-ascii characters

Also change test3.zip to trigger the bug if reversion
Use raw_id_fields in admin

Fixes #29
Move extra_data from base class to models

Only models that reflect GTFS files need extra data
Removed from Zone, Block, and Shape
It also looks better in the admin this way
On trip, change inbound/outbound to 0/1

GTFS uses to distinguish trips that have the route ID, but go in
different directions.  Outbound/Inbound are suggested interpretations,
not part of the spec.

Fixes #32.