Update to Hugo 0.53 and remove all .Site references (#12079)

* Remove all .Site variable references

* Update Hugo version in Travis CI config and Makefile

layouts/case-studies/list.html

@@ -1,6 +1,6 @@
 {{ define "main" }}
 {{ $pages := .Pages }}
-{{ with $.Site.Params.language_alternatives }}
+{{ with site.Params.language_alternatives }}
 {{ range . }}
        {{ with (where $.Translations ".Lang" . ) }}
        {{ $p := index . 0 }}      
@@ -65,4 +65,4 @@
 	<p class="quote">"{{ .page.Params.quote | html }}"</p>
 	<a href="{{ .page.RelPermalink }}"{{ if $isForeignLanguage }} target="_blank"{{ end }}>{{ T "main_read_about"}} {{ .page.LinkTitle }}</a>
 </div>
-{{ end }}
+{{ end }}