Refactor dashboard activities path

app/assets/javascripts/dispatcher.js

@@ -349,7 +349,9 @@ import Activities from './activities';
           shortcut_handler = new ShortcutsIssuable(true);
           break;
         case 'dashboard:activity':
-          new Activities();
+          import('./pages/dashboard/activity')
+            .then(callDefault)
+            .catch(fail);
           break;
         case 'projects:commit:show':
           new Diff();

app/assets/javascripts/pages/dashboard/activity/index.js

@@ -0,0 +1,3 @@
+import Activities from '~/activities';
+
+export default () => new Activities();