Refactoring speed and frequency calculation part of gtfs_ops.py so that it
doesn't write to CSV straight away, but returns dicts/lists containing the
relevant info first. This will help with using this info programatically if
desired.
Added ability to save a 'gtfs_origin_id' for route segs, and upgraded the
reading and writing to CSV part to do this.
Just cleaning up some max line widths.
Added ability to save a GTFS origin ID for stops in OSSTIP format (useful if
you need to match up info about original gtfs ids).
* Refined the formatting of avg headway and speed CSV headers so time periods
  past midnight are clearer.
* Added ability to sort the gtfs stop pair IDs in speed-extraction from GTFS
  functions (Useful when you need a canonical ordering for searching).
Created new MultipleTimePeriodsSegSpeedInfo and
MultipleTimePeriodsPerRouteSpeedModel classes.

The latter of which allows you to read in full speed details from a GTFS.

Updated the create_network_topology_from_existing_gtfs.py function to save
necessary origin gtfs route and stop IDs for above classes.

Updated create_gtfs_from_basicinfo.py to pass in extra info to SegSpeedModel
necessitated by new classes above, and to have a cmd-line option to allow you
to use the MultipleTimePeriodsPerRouteSpeedModel if a suitable origin GTFS
file is provided.

Created new cmd-line script to extract and avg speeds and headways
during fixed-width time periods of a GTFS, and save to files in a specified
directory (save_all_route_speeds_headways.py)