similar posts and cdn of mathjax

Author: TangMingliang95

_includes/head.html

@@ -50,7 +50,7 @@
 });
 </script>
 <script type="text/javascript"
-  src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
+  src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
 </script>
 {% endif %}
 </head>

_layouts/post.html

@@ -79,7 +79,9 @@ <h2 id="comments">Comments</h2>
                     Content
                 </div>
                 <ul id="content-side" class="content-ul">
+                    {% if hasSimilar.size > 0 %}
                     <li><a href="#similar_posts">Similar Posts</a></li>
+                    {% endif %}
                     <li><a href="#comments">Comments</a></li>
                 </ul>
             </div>