Adding a notification stack for error messages

app/assets/javascripts/components/reducers/index.jsx

@@ -3,10 +3,12 @@ import timelines           from './timelines';
 import meta                from './meta';
 import compose             from './compose';
 import follow              from './follow';
+import notifications       from './notifications';
 
 export default combineReducers({
   timelines,
   meta,
   compose,
-  follow
+  follow,
+  notifications
 });