Improve layout structure so users don't have to name posts "post"

By moving default to a page layout and posts to default, any section can
be a post. Some users were confused when they had posts that were not
named as such. No need to impose naming conventions on people.

layouts/_default/single.html

-{{ define "header" }}{{ partial "page-header.html" . }}{{ end }}
+{{ define "header" }}
+   {{/* We can override any block in the baseof file be defining it in the template */}}
+  {{ partial "page-header.html" . }}
+{{ end }}
+
 {{ define "main" }}
   <div class="flex-l mt2 mw8 center">
     <article class="center cf pv5 ph3 ph4-ns mw7">
-      <header>
-        <p class="f6 b helvetica tracked">
-          {{ humanize .Section | upper  }}
-        </p>
-        <h1 class="f1">
-          {{ .Title }}
-        </h1>
-      </header>
-      <div class="nested-copy-line-height lh-copy f4 nested-links nested-img mid-gray">
+      <p class="f6 b helvetica tracked">
+        {{/* Humanize removes hyphens and capitalizes the first word */}}
+        {{ humanize .Section | upper  }}
+      </p>
+      <h1 class="f1 athelas">
+        {{ .Title }}
+      </h1>
+        {{/* TODO: Add Hugo author  */}}
+        {{/* Hugo uses Go's date formatting is set by example. Here are two formats */}}
+      <time class="f6 mv4 dib tracked" datetime="{{ .Date.Format "2006-01-02T15:04:05Z07:00" }}">
+        {{ .Date.Format "January 2, 2006" }}
+      </time>
+      <section class="nested-copy-line-height lh-copy serif f4 nested-links nested-img mid-gray">
         {{ .Content }}
-      </div>
+      </section>
+      {{ partial "tags.html" . }}
     </article>
-    <aside class="ph3 mt2 mt6-ns">
+    <div class="ph3 mt2 mt6-ns">
       {{ partial "menu-contextual.html" . }}
-    </aside>
+    </div>
   </div>
 {{ end }}

layouts/page/single.html

+{{ define "header" }}{{ partial "page-header.html" . }}{{ end }}
+{{ define "main" }}
+  <div class="flex-l mt2 mw8 center">
+    <article class="center cf pv5 ph3 ph4-ns mw7">
+      <header>
+        <p class="f6 b helvetica tracked">this is the page temp
+          {{ humanize .Section | upper  }}
+        </p>
+        <h1 class="f1">
+          {{ .Title }}
+        </h1>
+      </header>
+      <div class="nested-copy-line-height lh-copy f4 nested-links nested-img mid-gray">
+        {{ .Content }}
+      </div>
+    </article>
+  </div>
+{{ end }}

layouts/post/single.html

-{{ define "header" }}
-   {{/* We can override any block in the baseof file be defining it in the template */}}
-  {{ partial "page-header.html" . }}
-{{ end }}
-
-{{ define "main" }}
-  <div class="flex-l mt2 mw8 center">
-    <article class="center cf pv5 ph3 ph4-ns mw7">
-      <p class="f6 b helvetica tracked">
-        {{/* Humanize removes hyphens and capitalizes the first word */}}
-        {{ humanize .Section | upper  }}
-      </p>
-      <h1 class="f1 athelas">
-        {{ .Title }}
-      </h1>
-        {{/* TODO: Add Hugo author  */}}
-        {{/* Hugo uses Go's date formatting is set by example. Here are two formats */}}
-      <time class="f6 mv4 dib tracked" datetime="{{ .Date.Format "2006-01-02T15:04:05Z07:00" }}">
-        {{ .Date.Format "January 2, 2006" }}
-      </time>
-      <section class="nested-copy-line-height lh-copy serif f4 nested-links nested-img mid-gray">
-        {{ .Content }}
-      </section>
-      {{ partial "tags.html" . }}
-    </article>
-    <div class="ph3 mt2 mt6-ns">
-      {{ partial "menu-contextual.html" . }}
-    </div>
-  </div>
-{{ end }}