0.8-2018-06-01

This release contain minor backwards incompatible changes. You should
update your code.

- (1) ``BaseDocumentViewSet`` (which from now on does not contain
      ``suggest`` functionality) has been renamed to ``DocumentViewSet``
      (which does contain ``suggest`` functionality).
- (2) You should no longer import from
      ``django_elasticsearch_dsl_drf.views``. Instead, import from
      ``django_elasticsearch_dsl_drf.viewsets``.

• Deprecated django_elasticsearch_dsl_drf.views in favour
  of django_elasticsearch_dsl_drf.viewsets.
• Suggest action/method has been moved to SuggestMixin class.
• FunctionalSuggestMixin class introduced which resembled functionality
  of the SuggestMixin with several improvements/additions, such as
  advanced filtering and context-aware suggestions.
• You can now define a default suggester in suggester_fields which will
  be used if you do not provide suffix for the filter name.