Switch to new MathJax CDN, closes #409

Author: wetneb

templates/dissemin/skeleton.html

@@ -41,7 +41,7 @@
       tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']]}
     });
     </script>
-    <script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML" async>
+    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML" async>
     </script>
     <script type="text/javascript" src="{% static "editing.js" %}"></script>
     <script type="text/javascript" src="{% static "name.js" %}"></script>