Support for subscriptions

[jackrr]

I'm setting up my first subscriptions using graphql-ruby and ActionCable. I'd like to be able to test out my implementation in graphiql before proceeding with consuming the new subscription API in my relay frontend app, but from a scan of this repo it doesn't seem possible at this time.

PS Thanks for making this and graphql-ruby. I could quickly get a graphql server in Rails thanks to these packages.

[keithmgould]

+1

[LeathanTeal]

+1

[EugeneGrigorenko]

+1