Fix download link (#64)

Author: easylogic

index.html

@@ -9,7 +9,7 @@
   <h1 class="text-center index-title">
     <span class="img-index-title"></span>
     <span class="img-index-title-mobile">Super Simple WYSIWYG<br>Editor on Bootstrap</span>
-    <a href="{{ site.repository }}/archive/master.zip" class="index-download">
+    <a href="{{ site.repository }}/releases/download/v{{ site.version }}/summernote-{{ site.version }}-dist.zip" class="index-download">
       <span class="img-index-download"></span>
     </a>
   </h1>