• RequestSchema is only needed in v2 to reject additional fields
• ResponseSchema is currently not playing too well with IDE (pycharm cough) because its missing a constructor with the kwargs (see ResponseSchema is missing constructor parameters #137)
• Having two to inherit from 2 schemas is not that nice since we use them a lot in requests and responses (see PR Improve "basics" docs #152)
• It's easy to forget and just use Schema from marshmallow (our doc does a poor job of recommending them too)

For those reasons I think we should refactor that into a single class that we use in all the tutorials and doc.