Correcting issue with cached i18n menu (#174)

* Create fr.toml

French translation

* Social link to "mastodon" added

* Some statics partials are cached, to optimise rendering

* Caching moved so that the i18n menu will work as expected. Refs #35

layouts/partials/page-header.html

   {{ $featured_image := (trim $featured_image "/") | absURL }}
   <header class="cover bg-top" style="background-image: url('{{ $featured_image }}');">
     <div class="pb3-m pb6-l bg-black-60">
-      {{ partialCached "site-navigation.html" . }}
+      {{ partial "site-navigation.html" . }}
       <div class="tc-l pv6 ph3 ph4-ns">
         {{ if not .Params.omit_header_text }}
           <h1 class="f2 f1-l fw2 white-90 mb0 lh-title">{{ .Title | default .Site.Title }}</h1>
 {{ else }}
   <header>
     <div class="{{ .Site.Params.background_color_class | default "bg-black" }}">
-      {{ partialCached "site-navigation.html" . }}
+      {{ partial "site-navigation.html" . }}
     </div>
   </header>
 {{ end }}

layouts/partials/site-header.html

   {{ $featured_image := (trim $featured_image "/") | absURL }}
   <header class="cover bg-top" style="background-image: url('{{ $featured_image }}');">
     <div class="{{ .Site.Params.cover_dimming_class | default "bg-black-60" }}">
-      {{ partialCached "site-navigation.html" .}}
+      {{ partial "site-navigation.html" .}}
       <div class="tc-l pv4 pv6-l ph3 ph4-ns">
         <h1 class="f2 f-subheadline-l fw2 white-90 mb0 lh-title">
           {{ .Title | default .Site.Title }}
 {{ else }}
   <header>
     <div class="pb3-m pb6-l {{ .Site.Params.background_color_class | default "bg-black" }}">
-      {{ partialCached "site-navigation.html" . }}
+      {{ partial "site-navigation.html" . }}
       <div class="tc-l pv3 ph3 ph4-ns">
         <h1 class="f2 f-subheadline-l fw2 light-silver mb0 lh-title">
           {{ .Title | default .Site.Title }}

layouts/partials/site-navigation.html

           {{ end }}
         </ul>
       {{ end }}
-      {{ partial "social-follow.html" . }}
+      {{ partialCached "social-follow.html" . }}
     </div>
   </div>
 </nav>