add import vue in readme

README.md

@@ -11,19 +11,20 @@ socket.io implemantation for Vuejs 2.0 and 1.0
   ``` bash
   npm install vue-socket.io@1.0.2 --save
   ```
-  
+
 ## Usage
 
 ``` js
+import Vue from 'vue';
 import VueSocketio from 'vue-socket.io';
 
 Vue.use(VueSocketio, 'http://socketserver.com:1923'); // Automaticly socket connect from url string
 
 /*
   import socketio from 'socket.io-client';
-  
+
   var ioInstance = socketio('http://socketserver.com:1923');
-  
+
   Vue.use(VueSocketio, ioInstance); // bind custom socketio instance
 */