subscriptions with graphiql

[cescoferraro]

I cannot use subscriptions with the graphical interface.
I tried to solve the issue with #69 but I still get

client.js:1603 WebSocket connection to 'ws://localhost:7000/subscriptions' failed: Error during WebSocket handshake: Sent non-empty 'Sec-WebSocket-Protocol' header but no response was received

the same code works with the playground. any pointers??