change header grid so the nav doesn’t look so squished

site/_includes/header.html

@@ -3,7 +3,7 @@
     {% include primary-nav-items.html %}
   </nav>
   <div class="grid">
-    <div class="unit one-third center-on-mobiles">
+    <div class="unit golden-small center-on-mobiles">
       <h1>
         <a href="{{ site.url }}/">
           <span>Jekyll</span>
@@ -11,7 +11,7 @@
         </a>
       </h1>
     </div>
-    <nav class="main-nav unit two-thirds hide-on-mobiles">
+    <nav class="main-nav unit golden-large hide-on-mobiles">
       {% include primary-nav-items.html %}
     </nav>
   </div>