add a loading indicator to history and pull requests

assets/javascripts/app/templates/builds/list.hbs

@@ -1,4 +1,5 @@
-<table id="builds" class="list">
+{{#if builds.isLoaded}}
+  <table id="builds" class="list">
     <thead>
       <tr>
         <th>{{t builds.name}}</th>
@@ -36,10 +37,13 @@
         {{/view}}
       {{/each}}
     </tbody>
-</table>
+  </table>
 
-<p>
+  <p>
     <button {{action showMore on="click" target="this" isVisibleBinding="hasMore"}}>
       {{t builds.show_more}}
     </button>
-</p>
+  </p>
+{{else}}
+  <div class="loading"><span>Loading</span></div>
+{{/if}}