Add protocol docs

PROTOCOL.md

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+# Skynet Protocol
+
+## General
+
+Connections are by websocket.
+Messages must be JSON-serialized objects containing at least a `type` key (e.g. `{"type": "log"}`) - this key is the command to run.
+Commands take other arguments, passed in that object (e.g. `{"type": "open", "channel": "whatever"}`).
+When a command is executed, it will either return a good result (e.g. `{"type": "result", "for": "log", "log": []}`) or an error (e.g. `{"type": "error", "error": "Human-readable description of error."}`).
+Clients may also receive events, which have a `type` key containing the name of the event and extra data (e.g. `{"type": "message", "channel": 42, "message": "hi"}`).
+
+## Client
+
+Available at `/connect`.
+This is the interface `client.lua` uses.
+
+### Commands
+
+#### open
+
+Takes a `channel` key (channel to open - can be string or number) and opens that channel on the socket sending this command. Opening `*` will listen to messages on all channels.
+
+Returns `channels`, a list of channels which are now open.
+
+#### close
+
+Takes a `channel` key and closes that channel - opposite of open.
+
+Returns `channels`, a list of channels which are now open.
+
+#### message
+
+Takes a `message` key (contents of message to send) and `channel` key (channel to send on) and sends the message to all clients listening on the channel used.  See `message` event for further details.
+
+Returns the message sent.
+
+### Events
+
+#### message
+
+This contains all the keys present in the message command which produced it (should always include `channel` and `message`) as well as `time` (as produced by `new Date().getTime()`) and `ID` (unique per-message ID).
+
+These are sent when another client uses the `message` command with a channel your socket is listening on.
+
+## Peer
+
+Coming Soon.