Use something smarter than `Show/Read` for the websockets protocol

I just tried to use `Data.Serialize` with generic deriving, but am stuck. While `Network.WebSockets` (the server side) has no problems sending binary data (as a `ByteString`) over the wire, the corresponding support in ghcjs, at , seems to be shaky. I might get a `Blob` out, but I do not see how to get a `ByteString` out.

I think I was at this point before, so I record this here.

Either I need to figure out how to work with `ByteString` in GHCJS, or use a different serialization library which targets `Data.Text`.

Start by reading the Network.WebSockets server-side binary-data path and ghcjs-base's JavaScript/Web/MessageEvent.hs, then compare the ByteString and Data.Text options mentioned in the issue. Done means the websocket protocol no longer depends on Show/Read and the chosen representation works across the server and GHCJS client.

Written by the indexing model from the issue text.