update index alert for darkly announcement

index.html

@@ -99,7 +99,7 @@
               </span>
             </div>
             <div class="alert alert-info">
-              Now you can grab HTML snippets from Bootswatch. <a href="http://news.bootswatch.com/post/78442060195/grab-html-snippets-from-bootswatch">Learn more...</a>
+              Introducing Darkly, a dark version of Flatly. <a href="http://news.bootswatch.com/post/79869499737/introducing-darkly">Learn more...</a>
             </div>
             <div class="row">
               <div class="col-md-6 col-md-offset-3">