_layouts, _sass: Add module-week to module-header

_layouts/module.html

 <div class="module">
-  <h3 class="module-header">{{ page.title }}</h3>
+  <h3 class="module-header"><strong class="module-week">{{ page.week }}</strong> {{ page.title }}</h3>
   {% if page.days %}
   <dl class="module-days">
     {% for day in page.days %}

_sass/custom/module.scss

@@ -10,6 +10,10 @@
   }
 }
 
+.module-week {
+  @extend .label, .text-grey-dk-100, .bg-grey-lt-200;
+}
+
 .module-date {
   @extend .card-header;
 }