Aborting pending requests

Hello!

I'm not sure if that's a responsibility of this lib or not but i'm building a search widget based on graphql server and graphql.js lib and was wondering - is there any way to abort/cancel pending request done by graphql.js?

Sometimes user changes his query during load of a previous query which generates two parallel requests and leads to weird results. It would be great to be able to run some `abort()` method on `mutate()` or `query()` instance to kill the request.

Thanks!