FEATURE: Show a button to Staff for "Moderation History" on posts/topics

When clicked, it pops up a modal showing a history of moderation actions
taken on the post or topic.

app/assets/javascripts/admin/controllers/modals/admin-moderation-history.js.es6

@@ -0,0 +1,18 @@
+import ModalFunctionality from 'discourse/mixins/modal-functionality';
+
+export default Ember.Controller.extend(ModalFunctionality, {
+  loading: null,
+  historyTarget: null,
+  history: null,
+
+  onShow() {
+    this.set('loading', true);
+    this.set('history', null);
+  },
+
+  loadHistory(target) {
+    this.store.findAll('moderation-history', target).then(result => {
+      this.set('history', result);
+    }).finally(() => this.set('loading', false));
+  }
+});