use 1.16 HAFAS protocol

[derhuerst]

PR for #3

[derhuerst]

The VBB endpoint does not support the numF parameter in combination with the new 1.16 protocol, it just fails with CGI_READ_FAILED. The numF parameter determines the number of journeys in the journeys() method.

There is a mechanism to get subsequent journeys by providing a certain key, but I haven't figured out how to use it yet. This means that, currently, we have no proper way to ensure a certain number of journeys. Technically, it would be a breaking change to remove the results option and just return the number of journeys that they provide, because people might expect hafas-client to return a certain number of journeys.

@deg0nz @jfilter @juliuste @blydro What do you think should be done? Release the (technically breaking change as 3.0.0, or just as 2.3.4?

[derhuerst]

I have figured it out. In the VBB case, I will let hafas-client send more requests to collect the number of results. Although this may lead to e.g. 10 requests to fulfill a single journeys() call, I can circumvent a breaking change.

Sorry for pinging you all.