no longer need to configure MathJax due to 2838faa426

exampleSite/layouts/partials/foot_custom.html

@@ -1,12 +1,4 @@
 <script src="//yihui.name/js/math-code.js"></script>
-<script type="text/x-mathjax-config">
-MathJax.Hub.Config({
-  tex2jax: {
-    inlineMath: [['$','$'], ['\\(','\\)']],
-    processEscapes: true
-  }
-});
-</script>
 <script async src="//cdn.bootcss.com/mathjax/2.7.1/MathJax.js?config=TeX-MML-AM_CHTML"></script>
 
 <script async src="//yihui.name/js/center-img.js"></script>