Change section name to section title in summary (#520)

* Change section name to section title

Mimics functionality in page.html. Fix #519

* Keep title as specified

* Include span in conditional

layouts/_default/summary.html

@@ -1,6 +1,6 @@
 <div class="relative w-100 mb4 bg-white nested-copy-line-height">
   <div class="bg-white mb3 pa4 gray overflow-hidden">
-    <span class="f6 db">{{ humanize .Section }}</span>
+    {{with .CurrentSection.Title }}<span class="f6 db">{{ . }}</span>{{end}}
     <h1 class="f3 near-black">
       <a href="{{ .RelPermalink }}" class="link black dim">
         {{ .Title }}