Add slashes to WebSocket protocol URL (facebook#8116)

Author: Baael

packages/react-dev-utils/webpackHotDevClient.js

@@ -64,6 +64,7 @@ var connection = new WebSocket(
  port: window.location.port,
  // Hardcoded in WebpackDevServer
  pathname: '/sockjs-node',
+ slashes: true,
  })
 );