Patch release with these changes:
- Update dependencies (#270)
- Change AsyncioExecutor loop argument type (#273)
- ExecutionResults can now be stringified (#277)
- Various mypy issues (#278)
- Minor fixes regarding the test suite
Note that the repository for GraphQL v2 has been renamed
from graphql-core to graphql-core-legacy.
The graphql-core repository is now used gor GraphQL v3.