tweak hero default behavior

layouts/partials/page-header.html

@@ -2,7 +2,7 @@
 {{ if $featured_image }}
   {{/* Trimming the slash and adding absURL make sure the image works no matter where our site lives */}}
   {{ $featured_image := (trim $featured_image "/") | absURL }}
-  <header class="cover bg-center" style="background-image: url('{{ $featured_image }}');">
+  <header class="cover bg-top" style="background-image: url('{{ $featured_image }}');">
     <div class="pb3-m pb6-l bg-black-60">
       {{ partial "site-navigation.html" . }}
       <div class="tc-l pv6 ph3 ph4-ns">

layouts/partials/site-header.html

@@ -1,8 +1,8 @@
-{{ $featured_image := .Params.featured_image | default .Site.Params.featured_image }}
+{{ $featured_image := .Params.featured_image }}
 {{ if $featured_image }}
   {{/* Trimming the slash and adding absURL make sure the image works no matter where our site lives */}}
   {{ $featured_image := (trim $featured_image "/") | absURL }}
-  <header class="cover bg-center" style="background-image: url('{{ $featured_image }}');">
+  <header class="cover bg-top" style="background-image: url('{{ $featured_image }}');">
     <div class="bg-black-60">
       {{ partial "site-navigation.html" .}}
       <div class="tc-l pv4 pv6-l ph3 ph4-ns">
@@ -10,7 +10,7 @@
           {{ .Title | default .Site.Title }}
         </h1>
         {{ with .Params.description }}
-          <h2 class="fw1 f5 f3-l white-80 mt3">
+          <h2 class="fw1 f5 f3-l white-80 measure-wide-l center mt3">
             {{ . }}
           </h2>
         {{ end }}