All API calls signatures have changed. Old situation:
<?php
$service->getArtist(1);
New situation is always using arrays:
<?php
$service->getArtist([
'id' => 1
]);
In the resources/service.php file you can find all the implemented calls and their signatures and responses.
It's not yet possible to iterate over the responses. Perhaps this will be added in the near future. It should be
easy to implement an Iterator yourself. PR's are welcome :).
Caching in the library itself is removed. This can be achieved by creating or using a cache plugin. At the moment of writing the plugin for Guzzle isn't refactored yet for version 4.0.
Models have been replaced with plain old arrays. Models were nice for typing but a hell to manage. All responses will
return an array. When you want to debug the output use $response->toArray().