bug 1173989, exhibit sets can't tell apart 5 and "5". Use "5".

Filed simile-widgets/exhibit#137 upstream on the
actual issue, but for now we're working around the problem by comparing
our status numbers to strings.

apps/shipping/templates/shipping/milestones.html

@@ -43,12 +43,12 @@ <h1>Milestones</h1>
         data-ex-href-subcontent="{% url 'shipping.views.milestone.about'  "{&#123;.code}}" %}"></a>
       </td>
       <td>
-        <span data-ex-if=".status = {{ Milestone.SHIPPED }}">
+        <span data-ex-if=".status = '{{ Milestone.SHIPPED }}'">
           <input type="button" {% if not perms.shipping.can_ship %}
           disabled="disabled"{% endif %}
           value="tweak" />
           <span>
-            <span data-ex-if=".status = {{ Milestone.UPCOMING }}">
+            <span data-ex-if=".status = '{{ Milestone.UPCOMING }}'">
               <input type="button" {% if not perms.shipping.can_open %}
               disabled="disabled"{% endif %}
               data-ex-onclick-subcontent="doForm('open','{&#123;.code}}')"