title: vue-i18n dynamic locale with promise doesn't update
body: <p>I am testing <code>vue-i18n</code> in order to implement it for my future projects. I have a separate system to handle the translations, so I got remote json files. <code>vue-i18n</code> have a system to fetch the locale using a promise, explainations  <a href="https://kazupon.github.io/vue-i18n/dynamic.html" rel="nofollow noreferrer">here</a>.</p>
  
  <p>I cannot use the fetch method because my files are outside so I got cross-origin troubles. Instead I do it with <code>vue-resource</code>, but I don't know why, when I set a new set of locale, it doesn't update automatically. bescause the default lang is <code>en</code>, when I load my <code>en</code> locale file, it does nothing. I have to change two times the <code>config.lang</code> to force update.</p>
  
  <p>Several things:</p>
  
  <ul>
  <li><p>A jsfiddle to test > <a href="http://jsfiddle.net/t4kdoqj7/3/" rel="nofollow noreferrer">http://jsfiddle.net/t4kdoqj7/3/</a> uncomment line 19 to reproduce the fix</p></li>
  <li><p>Maybe it's just due to a bad using of <code>vue-resource</code></p></li>
  <li><p>I couldn't create a <code>vue-i18n</code> tag...</p></li>
  </ul>
  
  <p>Thank you for your help !</p>