Revert "Order post excerpts on homepage"

This reverts commit e08c3b01.

Apparently this wasn't necessary? Everything is correctly ordered now.
I'll leave my modified index.html out until I can prove it's needed.

layouts/index.html

-{{ define "main" -}}
-<div class="posts">
-{{ range .Data.Pages.ByDate -}}
-<article class="post">
-  <h1 class="post-title">
-    <a href="{{ .Permalink }}">{{ .Title }}</a>
-  </h1>
-  <time datetime="{{ .Date.Format "2006-01-02T15:04:05Z0700" }}" class="post-date">{{ .Date.Format "Mon, Jan 2, 2006" }}</time>
-  {{ .Summary }}
-  {{ if .Truncated }}
-  <div class="read-more-link">
-    <a href="{{ .RelPermalink }}">Read More…</a>
-  </div>
-  {{ end }}
-</article>
-{{- end }}
-</div>
-{{- end }}