Move all layouts to platters theme

layouts/partials/site_nav.html

@@ -1,17 +0,0 @@
-{{- $currentPage := . -}}
-{{- $url := $.RelPermalink -}}
-<nav class="site bulleted">
-{{ with site.Menus.main }}
-    {{- range . -}}
-    <li>
-      <a
-        {{ if $currentPage.HasMenuCurrent "main" . }}
-          class="active"
-        {{ end }}
-        href="{{ .URL }}">
-        <span>{{ .Name }}</span>
-      </a>
-    </li>
-    {{- end -}}
-{{ end }}
-</nav>