Port libswarm/beam websocket impl to libchan

[smarterclayton]

I need to move moby/swarmkit#49 over and also fix the error with the websocket handler where a server close hangs the client.

[smarterclayton]

@dmcgowan do you have a WIP branch for the changes you were making to http2? I want to get the pull ported but figure it's safer to base on your newer stuff.

[dmcgowan]

There is currently no WIP branch, all my current changes are in master or in a PR against master.