Features and bugfixes to support BART

[elliottwilliams]

BART works! Here's an overview of the changes I made to Timetable to get it here:

New features:

• Added post_init member functions to all GTFS classes. These are called from field_mapper once a GTFS object is parsed, and are used to define substitutions. For example, BART don't have stop codes, but have reasonable stop IDs, so gtfs::stop::post_init() falls back to using id as code if no code exists.
• Support reading service availability from calendar.txt. This required adding logic to determine the weekday in DateTime.
• Runtime arguments for the server to connect to, and the GTFS source directory. This makes it much easier to switch agencies. I also print connection and error messages from the transport.

Bug fixes:

• Fixed a bug where every Visit in a result would get a reference to the same stop_time reference.
• Enabled DST prediction in DateTime::resolve(). I'm not entirely sure why this matters but it fixed off-by-one-hour errors for BART's data.
• The CSV parser can now handle CRLF line endings.

I've tested visits_between with Citybus haven't seen any regressions yet.

[elliottwilliams]

You're very welcome!

I just tried dropping SFMTA's data set in. I had to add one change to strip leading whitespace from tokens (they represent empty strings as " "), but otherwise it works great:

Their stop_times.txt is 47.6MB. Timetable takes almost 700MB to index this.

...but it's still got sub-millisecond lookups :)