v1.0.0rc1

• DjangoChannelsGraphqlWs has migrated to the recent versions of Django, Channels, and Graphene. All other Python dependencies updated.
• Server outputs a warning to the log when operation/resolver takes longer than specified timeout, which is one second by default. The settings GraphqlWsConsumer.warn_operation_timeout and GraphqlWsConsumer.warn_resolver_timeout allow to tune the timeout or even disable the warning at all.
• If exception raises from the resolver a response now contains a field "extensions.code" with a class name of the exception.
• Added support for async resolvers and middlewares.
• WARNING: This release is not backward compatible with previous ones! The main cause is a major update of Django, Channels, and Graphene, but there are some introduced by the library itself. In particular, context lifetime and content have changed. See README.md for details.