Fixed a bug in date parsing. GTFS specifies a format of yyyymmdd but the existing implementation was using the invariant culture patterns. Tests were working because the test swapped out the implementation for one that worked.
Removed the required field check for agency_id and route_desc as these are defined as optional in RTFS in routes.txt.
If the location type in stops.txt is unknown, don't fail, just return null. There are agency feeds out there that break this rule.
shape_pt_sequence is not a required field in trips.txt.