PERF: use handlebars rendering for user list

this shave topic list rendering on local down from 140ms to 100ms

app/assets/javascripts/discourse/helpers/handlebars.js.es6

@@ -0,0 +1,17 @@
+Handlebars.registerHelper('handlebars', function(property, options) {
+
+  var template = Em.TEMPLATES[property + ".raw"];
+  var params = options.hash;
+
+  if(params) {
+    for(var prop in params){
+      params[prop] = Em.Handlebars.get(this, params[prop]) || params[prop];
+    }
+  }
+
+  return new Handlebars.SafeString(template(params));
+});
+
+Handlebars.registerHelper('get', function(property) {
+  return Em.get(this, property);
+});

app/assets/javascripts/discourse/templates/list/topic_list_item.hbs

@@ -31,7 +31,7 @@
 <td class='category'>{{bound-category-link category showParent=true}}</td>
 {{/unless}}
 
-{{view 'posters-column' posters=posters}}
+{{handlebars 'posters_column' posters=posters}}
 
 {{posts-count-column topic=model class="num" action="showTopicEntrance"}}
 <td {{bind-attr class=":num :views viewsHeat"}}>{{number views numberKey="views_long"}}</td>

app/assets/javascripts/discourse/templates/posters_column.raw.hbs

@@ -0,0 +1,5 @@
+<td class='posters'>
+{{#each posters}}
+<a href="{{get "user.path"}}" data-user-card="{{this.user.username}}" class="{{get "extras"}}">{{avatar this usernamePath="user.username" imageSize="small"}}</a>
+{{/each}}
+</td>