Added function to calculate bus speeds in Melbourne based on Laurent's
spatial-dependent calculation of road speeds in peak hour.

Also added some error-checking of inputs.
Added a "ramped" timetable, especially for buses, that tries to deal with road
congestion during peak hours and transitions between peak->off-peak, and
vice-versa, better.
Removed file no longer necessary that originally helped with design.

Latest version of that script is now in
https://github.com/andybotting/ptv2gtfs anyway.