only include facebook js if facebook_like is true

.themes/classic/source/_includes/facebook_like.html

@@ -1,3 +1,4 @@
+{% if site.facebook_like %}
 <div id="fb-root"></div>
 <script>(function(d, s, id) {
   var js, fjs = d.getElementsByTagName(s)[0];
@@ -6,3 +7,4 @@
   js.src = "//connect.facebook.net/en_US/all.js#appId=212934732101925&xfbml=1";
   fjs.parentNode.insertBefore(js, fjs);
 }(document, 'script', 'facebook-jssdk'));</script>
+{% endif %}