Refactored and cleaned up partials

src/partials/tabs.html

@@ -20,12 +20,14 @@
   IN THE SOFTWARE.
 -->
 
-<!-- Tabs with outline (level denotes the active level) -->
-<nav class="md-tabs
-      {% if page.ancestors | length > 0 %}
-        md-tabs--active
-      {% endif %}"
-    data-md-component="tabs">
+<!-- Determine class according to level -->
+{% set class = "md-tabs" %}
+{% if page.ancestors | length > 0 %}
+  {% set class = "md-tabs md-tabs--active" %}
+{% endif %}
+
+<!-- Tabs with outline -->
+<nav class="{{ class }}" data-md-component="tabs">
   <div class="md-tabs__inner md-grid">
     <ul class="md-tabs__list">
       {% for nav_item in nav %}