Refactor Packetizer/Messsage/Dispatcher

[maxtaco]

Here's a refactor that I didn't get around to doing:

• packetizer uses framing byte to io.ReadFull the right amount of data out of the stream. Encapsulates this byte array in the Message object
• Message object parses itself into a 3- or 4-array
• Nuke the Transporter.ReadLock and the makeDecodeNext functions, since the data is already in the Message object
• Change decoding to decode from a buffer inside of the Message object; this is where it gets dicey, since it might be heavyweight to make a new decoder for each message. Might want to "borrow" a local one. Unsure.