Updated the create GTFS script to now read both stops and segment info
 from shapefiles, as per recent design discussions.

Tested it works for the simple one-route case in the sample_input directory
(about to add).
Some sample input for testing the script on, e.g. using command:

./create_gtfs_from_basicinfo.py --output=output/google_transit.zip
--segments=sample_input/Craig-Line-Test.shp
--stops=sample_input/Craig-stops-clip.shp --service='train'