Fix VDI4655 docs

[byte-bastler]

The VDI4655 code example in the documentation is not working with the current version of demandlib (v2.2.0). There are two reasons for this:

1. The house dictionary requires the summer_temperature_limit and winter_temperature_limit entries to be set in order to run the example. When these entries are not set, a KeyError is raised. Even if they become optional again in the future (I saw a change in another commit), it probably doesn't hurt to include them in the code example.

2. The vdi.Region() constructor no longer accepts a try_region parameter. It seems that climate is used instead.

These changes make the example executable again.

[p-snft]

Thank you. Looks like in #50, we only adjusted the example in the examples directory but not the one in the docstring.

Concerning 1: The docstring is meant for the upcoming release, but you are right: adding the parameters does not hurt.