title: Docsify search plugin not working, always return no reulst
body: <h2>problem descritpion</h2>
  
  <p>i try to use the search function of docsifyk, but it seems not working.</p>
  
  <h2>steps to reproduce</h2>
  
  <p>so i do these steps:
  (following the official docsify documentation)</p>
  
  <ol>
  <li>i run 'docsify init' in a directory, so it generate a 'index.html' and a 'README.md'.</li>
  <li>i add the code into 'index.html‘.</li>
  </ol>
  
  <pre class="lang-sh prettyprint-override"><code>&lt;script src="//unpkg.com/docsify/lib/plugins/search.min.js"&gt;&lt;/script&gt;
  </code></pre>
  
  <h2>current behavior</h2>
  
  <p>the page shows the search button, but whatever i type, it returns 'no result'.</p>
  
  <h2>other information</h2>
  
  <p>i have tried it on different computers(mac/ubuntu 16), both not working</p>
  
  <p>Did Anybody Ever Have The Same Question?</p>