Updating reading of route defs to read id properly

(route ID is now forced to int)
Updating to handle stop names properly in shp

Stop name field in shape files now read/written as "name".
(Note:- need to fix writing of this later, in another commit I already
have on file on another PC).
Push gtfs import to sublevel in seg_speed_models

(This helps for work on machines where you don't have gtfs transitfeed
library installed)
New script to allow trimming routes b/w stops

New script to allow trimming routes between certain stops. Here is a
copy of help:-

Usage: trim_routes.py [options]

Options:
-h, --help            show this help message and exit
--input_route_defs=INPUT_ROUTE_DEFS
CSV file listing name, directions, and segments of
each route.
--input_segments=INPUT_SEGMENTS
Shapefile of line segments.
--input_stops=INPUT_STOPS
Shapefile of stops.
--service=SERVICE     Should be one of 'bus', 'bus-motorway', 'train',
'tram'
--output_route_defs=OUTPUT_ROUTE_DEFS
CSV file (to create) listing name, directions, and
segments of each route.
--output_segments=OUTPUT_SEGMENTS
(Output) shapefile of line segments.
--route_trim_spec_csv=ROUTE_TRIM_SPEC_CSV
Path to CSV file containing list of routes to trim,
and stops to trim between.
Making csv writing work better on Windows

... and also keeping Python 3 compatible.