Drop support for scalar 'author' configuration

_config.yml

@@ -1,6 +1,7 @@
 title: Your awesome title
-author: GitHub User
-email: your-email@domain.com
+author:
+  name: GitHub User
+  email: your-email@domain.com
 description: > # this means to ignore newlines until "show_excerpts:"
   Write an awesome description for your new site here. You can edit this
   line in _config.yml. It will appear in your document head meta (for
@@ -46,7 +47,7 @@ minima:
     #   instance: example.com
     # - username: jekyll2
     #   instance: example.com
-    
+
 # If you want to link only specific pages in your header, uncomment
 # this and add the path to the pages in order as they should show up
 #header_pages:

_includes/footer.html

@@ -6,14 +6,16 @@
     <div class="footer-col-wrapper">
       <div class="footer-col">
         <h2 class="footer-heading">{{ site.title | escape }}</h2>
+      {%- if site.author %}
         <ul class="contact-list">
-          {% if site.author -%}
-            <li class="p-name">{{ site.author | escape }}</li>
+          {% if site.author.name -%}
+            <li class="p-name">{{ site.author.name | escape }}</li>
           {% endif -%}
-          {% if site.email -%}
-            <li><a class="u-email" href="mailto:{{ site.email }}">{{ site.email }}</a></li>
+          {% if site.author.email -%}
+            <li><a class="u-email" href="mailto:{{ site.author.email }}">{{ site.author.email }}</a></li>
           {%- endif %}
         </ul>
+      {%- endif %}
       </div>
       <div class="footer-col">
         <p>{{ site.description | escape }}</p>