Bring all MathJax logic into one common template

Might as well do this right away, we're here anyway.

templates/collection-post.tmpl

@@ -30,21 +30,11 @@
 		{{range .Images}}<meta property="og:image" content="{{.}}" />{{else}}<meta property="og:image" content="{{.Collection.AvatarURL}}">{{end}}
 		<meta property="article:published_time" content="{{.Created8601}}">
 		{{if .Collection.StyleSheet}}<style type="text/css">{{.Collection.StyleSheetDisplay}}</style>{{end}}
-		{{if .Collection.RenderMathJax}}
-		<script type="text/x-mathjax-config">
-		  MathJax.Hub.Config({
-			extensions: ["tex2jax.js"],
-			jax: ["input/TeX", "output/HTML-CSS"],
-			tex2jax: {
-			  inlineMath: [ ['$','$'], ["\\(","\\)"] ],
-			  displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
-			  processEscapes: true
-			},
-			"HTML-CSS": { fonts: ["TeX"] }
-		  });
-		</script>
-		<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML" async></script>{{end}}
 
+		{{if .Collection.RenderMathJax}}
+		  <!-- Add mathjax logic -->
+  		  {{template "mathjax" . }}
+		{{end}}
 
 		<!-- Add highlighting logic -->
 		{{template "highlighting" .}}

templates/collection-tags.tmpl

@@ -30,20 +30,11 @@
 		<meta property="og:url" content="{{.CanonicalURL}}tag:{{.Tag}}" />
 		<meta property="og:image" content="{{.Collection.AvatarURL}}">
 		{{if .Collection.StyleSheet}}<style type="text/css">{{.Collection.StyleSheetDisplay}}</style>{{end}}
+
 		{{if .Collection.RenderMathJax}}
-		<script type="text/x-mathjax-config">
-		  MathJax.Hub.Config({
-			extensions: ["tex2jax.js"],
-			jax: ["input/TeX", "output/HTML-CSS"],
-			tex2jax: {
-			  inlineMath: [ ['$','$'], ["\\(","\\)"] ],
-			  displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
-			  processEscapes: true
-			},
-			"HTML-CSS": { fonts: ["TeX"] }
-		  });
-		</script>
-		<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML" async></script>{{end}}
+		  <!-- Add mathjax logic -->
+		  {{template "mathjax" .}}
+		{{end}}
 
 		<!-- Add highlighting logic -->
 		{{template "highlighting" . }}

templates/collection.tmpl

@@ -27,22 +27,12 @@
 		<meta property="og:url" content="{{.CanonicalURL}}" />
 		<meta property="og:description" content="{{.Description}}" />
 		<meta property="og:image" content="{{.AvatarURL}}">
-		{{if .StyleSheet}}<style type="text/css">{{.StyleSheetDisplay}}</style>{{end}}
-		{{if .RenderMathJax}}
-		<script type="text/x-mathjax-config">
-		  MathJax.Hub.Config({
-			extensions: ["tex2jax.js"],
-			jax: ["input/TeX", "output/HTML-CSS"],
-			tex2jax: {
-			  inlineMath: [ ['$','$'], ["\\(","\\)"] ],
-			  displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
-			  processEscapes: true
-			},
-			"HTML-CSS": { fonts: ["TeX"] }
-		  });
-		</script>
-		<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML" async></script>{{end}}
+		  {{if .StyleSheet}}<style type="text/css">{{.StyleSheetDisplay}}</style>{{end}}
 
+		{{if .RenderMathJax}}
+		  <!-- Add mathjax logic -->
+		  {{template "mathjax" .}}
+		{{end}}
 
 		<!-- Add highlighting logic -->
 		{{template "highlighting" . }}

templates/include/render.tmpl

@@ -2,7 +2,8 @@
 {{define "highlighting"}}
   <!-- TODO: make this conditional on presence of code blocks -->
   <link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.13.1/styles/atom-one-light.min.css"/>
-  <script src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.13.1/highlight.min.js" type="text/javascript"></script>
+  <script type="text/javascript"
+	  src="//cdnjs.cloudflare.com/ajax/libs/highlight.js/9.13.1/highlight.min.js" async></script>
 
   <script>
   addEventListener('load', function () {
@@ -12,3 +13,21 @@
       }});
   </script>
 {{end}}
+
+<!-- Include mathjax configuration -->
+{{define "mathjax"}}
+<script type="text/x-mathjax-config">
+  MathJax.Hub.Config({
+    extensions: ["tex2jax.js"],
+    jax: ["input/TeX", "output/HTML-CSS"],
+    tex2jax: {
+      inlineMath: [ ['$','$'], ["\\(","\\)"] ],
+      displayMath: [ ['$$','$$'], ["\\[","\\]"] ],
+      processEscapes: true
+    },
+    "HTML-CSS": { fonts: ["TeX"] }
+  });
+</script>
+<script type="text/javascript"
+	src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.5/MathJax.js?config=TeX-MML-AM_CHTML" async></script>
+{{end}}