make masthead translatable

_includes/masthead.html

@@ -4,7 +4,9 @@
       <nav id="site-nav" class="greedy-nav">
         <ul class="visible-links">
           <li class="masthead__menu-item masthead__menu-item--lg"><a href="{{ '/' | absolute_url }}">{{ site.title }}</a></li>
-          {% for link in site.data.navigation.main %}
+          {% assign split_path = page.path | split: "/" %}
+          {% assign locale = split_path[1] %}
+          {% for link in site.data.navigation[locale].main %}
             {% if link.url contains 'http' %}
               {% assign domain = '' %}
             {% else %}