Fixed the streaming API

Yesterday the streaming API was working great but suddenly it stop working.

I joined #mtgox @ freenode and a developer told me that there was a bug and I would need to set the `Origin` header by hand.

After changing that it continue failing so I compared the request generated by XChange and goxtool. There was an issue with the protocol to be used. To solve that, I changed from `draft_10` to `draft_17`.