Don't handle websocket upgrades if proxy.ws not present

Author: Shane Osbourne

lib/server/proxy-server.js

@@ -29,9 +29,11 @@ module.exports = function createProxyServer (bs, scripts) {
     bs.proxy.app.use(bs.options.getIn(["scriptPaths", "path"]),      scripts);
 
     /**
-     * Also proxy upgrades for Web Socket support
+     * Also proxy upgrades for Web Socket support if proxy.ws given
      */
-    proxy.server.on("upgrade", bs.proxy.app.handleUpgrade);
+    if (bs.options.getIn(["proxy", "ws"])) {
+        proxy.server.on("upgrade", bs.proxy.app.handleUpgrade);
+    }
 
     return proxy;
 };