Fix #5 handle standard "author: name" in YAML

inst/bulma/bulma.html

             $for(author)$
               <div class="level-item has-text-centered">
                 <div>
-                $if(author.name)$
                   <p class="title is-5">
                     $if(author.url)$
                       <a href="$author.url$">$author.name$</a>
                     $else$
-                      $author.name$
+                      $if(author.name)$$author.name$$else$$author$$endif$
                     $endif$
                   </p>
-                $endif$
                 $if(author.extra)$
                   <p class="subtitle is-6">
                     $for(author.extra)$$author.extra$$sep$<br>$endfor$