Made OBA stop sequence is 0 based

It's not 1 based, as originally thought
Made TripId unique

There are cases where two buses are on the same trip. Having two
updates for one trip is invalid, so just use the most recent bus to
checkin. Need to investigate this case more.
Merge pull request #37 from bschoenfeld/oba-patches

Fixed issues with OBA real time GTFS feed. This stuff was missed in #35.