message: async load mathjax
diff: <link href='https://fonts.googleapis.com/css?family=Open+Sans:400,600,300,700' rel='stylesheet' type='text/css'>
  <link rel="stylesheet" href="{{content-for "assetsPrefix"}}assets/vendor.css" class="notranslate">
  <link rel="stylesheet" href="{{content-for "assetsPrefix"}}assets/ember-osf-web.css" class="notranslate">
  - <script type="text/javascript"
  - src="//cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
  - </script>
  <script type="text/x-mathjax-config">
  MathJax.Hub.Config({
  tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']], processEscapes: true},
  skipStartupTypeset: true
  });
  </script>
  + <script type="text/javascript" async
  + src="//cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
  + </script>
  {{content-for "head"}}
  {{content-for "head-footer"}}
  </head>
  