Adds support for GTFS-realtime VehiclePosition feeds via a -p command

line parameter.

Tested using GTFS-realtime Vehicle Positions feed for HART buses in Tampa, Florida:
http://onebusaway.forest.usf.edu:8088/vehicle-positions

(View this feed in plain text here):
http://onebusaway.forest.usf.edu:8088/vehicle-positions?debug

Example usage:
gtfsrdb.py -p http://onebusaway.forest.usf.edu:8088/vehicle-positions -d sqlite:///test.db -c

I edited these attached Python files in Eclipse, not sure why its showing a deletion and addition of the entire files.  If you want me to go back and see if I can clean this up let me know.