storing WebSocket instance into @websocket instance variable, a try to fix #60

Not sure why `@socket` should be `nil` here...
https://github.com/celluloid/reel/blob/master/lib/reel/connection.rb#L60

It is there since v0.2.0.pre (read before my updates :))
https://github.com/celluloid/reel/blob/v0.2.0.pre/lib/reel/connection.rb#L62

No time to investigate why it should be `nil`, but setting it to actual `WebSocket` instance result into Stream Closed exception.

As a workaround we can store `WebSocket` instance into `@websocket` instance variable and use it instad of `@socket` on websocket requests?

This is fixing #60

Makes sense?