<!DOCTYPE html>
<html prefix="og: http://ogp.me/ns#">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="description" content="">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="author" content="">

    {{content-for "head"}}

    <link href='https://fonts.googleapis.com/css?family=Open+Sans:400,600,300,700' rel='stylesheet' type='text/css'>

    {{content-for "head-footer"}}
    <script type="text/javascript"
        src="//cdnjs.cloudflare.com/ajax/libs/mathjax/2.6.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
    </script>
    <script type="text/x-mathjax-config">
        MathJax.Hub.Config({
            tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']], processEscapes: true},
            skipStartupTypeset: true
        });
    </script>
  </head>
  <body>
    {{content-for "body"}}

    {{content-for "cdn"}}

    {{content-for "assets"}}

    {{content-for "raven"}}

    {{content-for "body-footer"}}
  </body>
</html>

<!DOCTYPE html>
<html prefix="og: http://ogp.me/ns#">
  <head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="description" content="">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="author" content="">

    {{content-for "head"}}

    <link href='https://fonts.googleapis.com/css?family=Open+Sans:400,600,300,700' rel='stylesheet' type='text/css'>

    {{content-for "head-footer"}}
    <script type="text/javascript"
        src="//cdnjs.cloudflare.com/ajax/libs/mathjax/2.6.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML">
    </script>
    <script type="text/x-mathjax-config">
        MathJax.Hub.Config({
            tex2jax: {inlineMath: [['$','$'], ['\\(','\\)']], processEscapes: true},
            skipStartupTypeset: true
        });
    </script>
    <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.6.3/css/font-awesome.css" rel="stylesheet" type="text/css">
  </head>
  <body>
    {{content-for "body"}}

    {{content-for "cdn"}}

    {{content-for "assets"}}

    {{content-for "raven"}}

    {{content-for "body-footer"}}
  </body>
</html>

Add font-awesome CDN to head of html.
Add font-awesome CDN to head of html.
