Bug fixes, new parameter definition, new option for near stations

The release includes some bug fixes and fixes for tests.

Besides that it is now possible to use the enumeration names themselves for parameters e.g. "climate_summary" instead of "kl" to define those parameters. Also the function get_nearby_stations (former get_nearest_station) has now an argument "max_distance_in_km" to select stations based on distance instead of simple ranking.

Initial release

The first release of wetterdienst. The release brings a new name, updates to the readme, a changelog, etc...