Reduce the depth of the DOM and simplify the CSS a bit

Remove the main intermediate container. It wasn't acutally serving a purpose.
Remove some of the BEM-style classes that also weren't really doing anything.

layouts/_default/taxonomy.html

@@ -1,14 +1,12 @@
 {{ define "main" }}
-  <main class="main--list taxonomy" data-taxonomy-name="{{ .Data.Singular }}">
+  <main class="main--list  taxonomy" data-taxonomy-name="{{ .Data.Singular }}">
     <header class="page-header">
       {{ partial "page_header.html" (dict "page" . "title" .Title) }}
     </header>
 
-    {{ with .Content -}}
-      <div class="main--list__content">{{ . }}</div>
-    {{- end }}
+    {{- .Content -}}
 
-    <div class="main--list__page-list">
+    <div class="main__page-list">
       {{ range .Pages.ByTitle }}
         {{ .Render "page_summary" }}
       {{ end }}