Added Websocket support.

Added Websocket support through proxy server.

Author: jcoady

labextension/vpython/src/glowcommlab.d.ts

@@ -1,3 +1,3 @@
 export function onmessage (msg: any): void;
-export function setupWebsocket (msg: any): void;
+export function setupWebsocket (msg: any, serviceUrl: any): void;
 export var comm: any;