title: django-cors-headers CORS_ORIGIN_WHITELIST tuple vs string issue
body: <p>I'm trying to use django-cors-headers for my project.</p>
  
  <p>It appears when I set CORS_ORIGIN_WHITELIST as a string it works fine. But when I use it as a tuple it doesn't work. Any idea why? I can't find anything specific in the documentation about the difference between using a tuple or string.</p>
  
  <p>To load the JSON I'm using jQuery $.getJSON()</p>
  
  <pre><code>$.getJSON( "http://127.0.0.1:8000/accounts/api_r/44234138/?format=json", function( data ) {
    var items = [];
    $.each( data, function( key, val ) {
      items.push( "&lt;li id='" + key + "'&gt;" + val + "&lt;/li&gt;" );
    });
  
    $( "&lt;ul/&gt;", {
      "class": "my-new-list",
      html: items.join( "" )
    }).appendTo( "#foo" );
  });
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/GORJc.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/GORJc.png" alt="Using CORS_ORIGIN_WHITELIST as a tuple"></a></p>
  
  <p><a href="https://i.stack.imgur.com/lcB7b.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/lcB7b.png" alt="Using CORS_ORIGIN_WHITELIST as a string"></a></p>