Update isort from 4.3.13 to 4.3.15 (#595)
Update isort from 4.3.13 to 4.3.15 (#595)


django-json-api/django-rest-framework-json-api,leo-naeka/django-rest-framework-json-api,django-json-api/rest_framework_ember,django-json-api/django-rest-framework-json-api