Fixes #53: Fixes 'Comments' view in Offline Mode

While working on the REST fallback for offline mode, I neglected to
refactor item fetching for the newer promises model. This mean’t we
weren’t correctly populating stores that would be used in this mode.
This has been confirmed as now working with this fix. Deploy with fix
running at https://react-hn-comments.appspot.com/

Author: addyosmani

src/services/HNServiceRest.js

@@ -25,6 +25,12 @@ function itemRef(id) {
   return fetch(endPoint + '/item/' + id + '.json', options)
 }
 
+function itemRefJSON(id) {
+  return itemRef(id).then(function(response) {
+    return response.json()
+  })
+}
+
 function userRef(id) {
   return fetch(endPoint + '/user/' + id + '.json', options)
 }
@@ -34,22 +40,23 @@ function updatesRef() {
 }
 
 function fetchItem(id, cb) {
-  itemRef(id).once('value', function(snapshot) {
-    cb(snapshot.val())
+  itemRef(id).then(function(snapshot) {
+    cb(snapshot)
   })
 }
 
 function fetchItems(ids, cb) {
   var items = []
+  var promises = []
   ids.forEach(function(id) {
-    fetchItem(id, addItem)
+    promises.push(itemRefJSON(id))
   })
-  function addItem(item) {
-    items.push(item)
+  Promise.all(promises).then(function(values) {
+    items = values
     if (items.length >= ids.length) {
       cb(items)
     }
-  }
+  })
 }
 
 module.exports = {