Incompatibility with new graphql-core resolvers API

[messa]

Hi! The tests are now failing - see a Travis build from my just-forked repository: https://travis-ci.org/messa/graphql-relay-py/builds/485088298

GraphQLLocatedError("<lambda>() got an unexpected keyword argument 'first'",)

I think the major cause of the errors is the API change in graphql-core v2.0.0:

New resolvers API. Moving from resolver(root, args, context, info) to resolver(root, info, **args)

It would be possible to limit versions of the graphql-core depency below 2.0.0 (it's now 'graphql-core>=0.5.0'), but I think that would be not very nice.

Would you accept a pull request that updates the code to the new resolver API?

[Cito]

This has been fixed in v2.0, so this issue can be closed.