Move some files to a better place, remove some unused file

layouts/partials/posts/disqus.html

@@ -0,0 +1,3 @@
+{{- if and (not (eq .Site.DisqusShortname "" )) (eq (.Site.Params.disable_comments | default false) false) -}}
+  {{ template "_internal/disqus.html" . }}
+{{- end -}}

layouts/partials/posts/math.html

@@ -0,0 +1,24 @@
+{{- if .Params.math -}}
+  <script type="text/javascript" async
+    src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.4/MathJax.js?config=TeX-AMS-MML_HTMLorMML-full">
+    MathJax.Hub.Config({
+      tex2jax: {
+        inlineMath: [['$','$']],
+        displayMath: [['$$','$$']],
+        processEscapes: true,
+        processEnvironments: true,
+        skipTags: ['script', 'noscript', 'style', 'textarea', 'pre'],
+        TeX: { extensions: ["AMSmath.js", "AMSsymbols.js"] }
+      }
+    });
+    MathJax.Hub.Queue(function() {
+      // Fix <code> tags after MathJax finishes running. This is a
+      // hack to overcome a shortcoming of Markdown. Discussion at
+      // https://github.com/mojombo/jekyll/issues/199
+      var all = MathJax.Hub.getAllJax(), i;
+      for(i = 0; i < all.length; i += 1) {
+          all[i].SourceElement().parentNode.className += ' has-jax';
+      }
+    });
+  </script>
+{{- end -}}

layouts/partials/posts/series.html

@@ -0,0 +1,24 @@
+{{ $currentPageUrl := .URL }}
+{{ if .Params.series }}
+<section class="see-also">
+  {{ range .Params.series }}
+    <h3>See also in {{ . }}</h3>
+    {{ $name := . | urlize }}
+    {{ $series := index $.Site.Taxonomies.series $name }}
+    {{ if gt (len $series.Pages) 0 }}
+      <nav>
+        <ul>
+        {{ $maxItems := $.Site.Params.maxSeeAlsoItems | default 5 }}
+        {{ range first (add $maxItems 1) $series.Pages }}
+          {{ if ne .URL $currentPageUrl }}
+            <li>
+              <a href="{{ .Params.ExternalLink | default .URL }}">{{ .Title }}</a>
+            </li>
+          {{ end }}
+        {{ end }}
+        </ul>
+      </nav>
+    {{ end }}
+  {{ end }}
+</section>
+{{ end }}