FEATURE: Include a user's pending posts in the topic view

Also includes a refactor to TopicView's serializer which was not
building our attributes using serializers properly.

test/javascripts/acceptance/composer-test.js.es6

@@ -255,6 +255,8 @@ QUnit.test("Posting on a different topic", async assert => {
 QUnit.test("Create an enqueued Reply", async assert => {
   await visit("/t/internationalization-localization/280");
 
+  assert.notOk(find(".pending-posts .reviewable-item").length);
+
   await click("#topic-footer-buttons .btn.create");
   assert.ok(exists(".d-editor-input"), "the composer input is visible");
   assert.ok(!exists("#reply-title"), "there is no title since this is a reply");
@@ -270,6 +272,8 @@ QUnit.test("Create an enqueued Reply", async assert => {
 
   await click(".modal-footer button");
   assert.ok(invisible(".d-modal"), "the modal can be dismissed");
+
+  assert.ok(find(".pending-posts .reviewable-item").length);
 });
 
 QUnit.test("Edit the first post", async assert => {

test/javascripts/fixtures/topic.js.es6

@@ -1,6 +1,7 @@
 /*jshint maxlen:10000000 */
 export default {
   "/t/280/1.json": {
+    pending_posts: [],
     post_stream: {
       posts: [
         {

test/javascripts/helpers/create-pretender.js.es6

@@ -430,7 +430,14 @@ export default function() {
       }
 
       if (data.raw === "enqueue this content please") {
-        return response(200, { success: true, action: "enqueued" });
+        return response(200, {
+          success: true,
+          action: "enqueued",
+          pending_post: {
+            id: 1234,
+            raw: data.raw
+          }
+        });
       }
 
       return response(200, {