title: issue with JSZip 3.0
body: <p>I have an error with JSZip 3.0. I am making a code for creating and download zip for that I am using the JSZip library.</p>
  
  <p>and my code to create a zip is given below.</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var zip = new JSZip();
  var urls = ["image/Screenshot (11).png","image/Screenshot (10).png"];
  var count = 0;
  var zipFilename = "zipFilename.zip";
  urls.forEach(function(url){
    var filename = "filename";
    JSZipUtils.getBinaryContent(url, function (err, data) {
       if(err) {
          throw err; // or handle the error
       }
       zip.file(filename, data, {binary:true});
       count++;
       if (count == urls.length) {
         var zipFile = zip.generate({type: "blob"});
         saveAs(zipFile, zipFilename);
       }
    });
  });</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="https://cdnjs.cloudflare.com/ajax/libs/jszip/3.2.1/jszip.min.js"&gt;&lt;/script&gt;
  &lt;script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/jszip-utils/0.1.0/jszip-utils.js"&gt;&lt;/script&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>with that I have received error <code>Uncaught Error: Error: This method has been removed in JSZip 3.0, please check the upgrade guide. at XMLHttpRequest.xhr.onreadystatechange</code> </p>
  
  <p>when I research this error I have found one answer <a href="https://gis.stackexchange.com/questions/242927/how-fix-error-this-method-has-been-removed-in-jszip-3-0-please-check-the-upgra">This</a> but I don't understand how and where can I use this.</p>
  
  <p>can anybody help me with this.</p>