Clean up CSS

- Add vim folds to make organized sections
- Rename a lot of classes from post- to page-
- Generalize series CSS classes better
- Clean up navbar div structure
- Remove langpicker and most of multilingual support
- many other minor tweaks

layouts/partials/page-list.html

@@ -1,7 +1,7 @@
 <div class="page-list">
     {{ with . }}
         {{ range . }}
-            <article class="post">
+            <article class="page">
                 {{ .Render "summary" }}
             </article>
         {{ end }}