Create EchoStream, used by clients to render local echo messages.
Move client.js:echo() into EchoStream. EchoStream.pushLine should throw an exception and disallow using pushLine() directly. EchoStream.echo() should call MudStream.pushLine with the rendered text.
Create EchoStream, used by clients to render local echo messages.
Move client.js:echo() into EchoStream. EchoStream.pushLine should throw an exception and disallow using pushLine() directly. EchoStream.echo() should call MudStream.pushLine with the rendered text.