Change some span tags to data attributes

Author: marocchino

_layouts/default.html

@@ -52,5 +52,6 @@ <h2>Comments</h2>
         <p>Published with <a href="http://svperstarz.github.io/jekyll-docs-ko/">Jekyll</a></p>
       </footer>
     </div>
+    <script src="javascripts/main.js" type="text/javascript"></script>
   </body>
 </html>