Update README.md (#271)

Author: Grawl

README.md

@@ -58,6 +58,7 @@ import Vue from 'vue'
 import store from './store'
 import App from './App.vue'
 import VueSocketIO from 'vue-socket.io'
+import SocketIO from 'socket.io-client'
 
 const options = { path: '/my-app/' }; //Options object to pass into SocketIO