replace holder.js references in dashboard example with placeholder gif. fixes twbs#16699

Author: mdo

docs/examples/dashboard/index.html

@@ -82,22 +82,22 @@ <h1 class="page-header">Dashboard</h1>
 
           <div class="row placeholders">
             <div class="col-xs-6 col-sm-3 placeholder">
-              <img data-src="holder.js/200x200/auto/sky" class="img-responsive" alt="Generic placeholder thumbnail">
+              <img src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" width="200" height="200" class="img-responsive" alt="Generic placeholder thumbnail">
               <h4>Label</h4>
               <span class="text-muted">Something else</span>
             </div>
             <div class="col-xs-6 col-sm-3 placeholder">
-              <img data-src="holder.js/200x200/auto/vine" class="img-responsive" alt="Generic placeholder thumbnail">
+              <img src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" width="200" height="200" class="img-responsive" alt="Generic placeholder thumbnail">
               <h4>Label</h4>
               <span class="text-muted">Something else</span>
             </div>
             <div class="col-xs-6 col-sm-3 placeholder">
-              <img data-src="holder.js/200x200/auto/sky" class="img-responsive" alt="Generic placeholder thumbnail">
+              <img src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" width="200" height="200" class="img-responsive" alt="Generic placeholder thumbnail">
               <h4>Label</h4>
               <span class="text-muted">Something else</span>
             </div>
             <div class="col-xs-6 col-sm-3 placeholder">
-              <img data-src="holder.js/200x200/auto/vine" class="img-responsive" alt="Generic placeholder thumbnail">
+              <img src="data:image/gif;base64,R0lGODlhAQABAIAAAHd3dwAAACH5BAAAAAAALAAAAAABAAEAAAICRAEAOw==" width="200" height="200" class="img-responsive" alt="Generic placeholder thumbnail">
               <h4>Label</h4>
               <span class="text-muted">Something else</span>
             </div>