Added handling of the sets conversion.
Since this library is to be kept light-weight, no "hack" was created for nested classes - in order for the classes to be hash-able inside the set, the user has to implement the hash functionality of the class. For reference, check "_test_from_dict_with_nested_set_classes_" test inside collection tests
Added handling of the sets conversion. Since this library is to be kept light-weight, no "hack" was created for nested classes - in order for the classes to be hash-able inside the set, the user has to implement the hash functionality of the class. For reference, check "_test_from_dict_with_nested_set_classes_" test inside collection tests