Add support for transfers #115
Description
First of all, I really appreciate the great work on this library!
The GTFS spec allows for an optional transfers.txt for specifying transfers between stops, see gtfs.org spec for transfers.txt
It would be great if this library could parse them as well.
I already took a stab at implementing this, I will open a PR so that if you want to and have time for it you could have a look and give your thoughts/feedback on it :)