Various bugfixes for the gtfsToTimetableApi example code

[hallonstedt]

• Update README with valid links to how API-keys are created
• Update requirements.txt to allow for more modern versions of libraries needed. I have tested them and they work fine.
• Add window start and end to the query_engine calls since default arguments only evaluate when the function is defined which previously meant that the departure window was static.
• The static time-table files were only loaded on application start instead of every 24 hours as intended. They are now checked on ever end-point call and if expired, they will be updated. This means a few milliseconds additional delay to API-calls but should not be noticeable.
• if GtfsTimeTable.py is run directly, it didn't use the command-line provided stop_id. This is now fixed.