Update README - require package only development

Author: ktquez

README.md

@@ -17,9 +17,9 @@ yarn add -D vue-axe
 ## Install plugin 
 ```javascript
 import Vue from 'vue'
-import VueAxe from 'vue-axe'
 
 if (process.env.NODE_ENV !== 'production') {
+  const VueAxe = require('../vue-axe')
   Vue.use(VueAxe, {
     config: {
       // ...