Fixed ember resolver warning for ambiguous authorNames access

no issue
- we've added an `{{author-names}}` helper, this generated a warning from `{{gh-posts-list-item}}` which contained `{{authorNames}}` referencing a CP on the component context
- changing the CP access to be explicit using `{{this.authorNames}}` resolves the warning
- updated other references in the template to be explicit in order to differentiate between local context and helpers (this will be enforced in later Ember versions)

app/templates/components/gh-posts-list-item.hbs

@@ -1,34 +1,38 @@
-<h3 class="gh-content-entry-title">{{#link-to "editor.edit" post.displayName post.id class="permalink" title="Edit this post"}}{{post.title}}{{/link-to}}</h3>
-<p>{{subText}}</p>
+<h3 class="gh-content-entry-title">
+    {{#link-to "editor.edit" this.post.displayName this.post.id class="permalink" title="Edit this post"}}
+        {{this.post.title}}
+    {{/link-to}}
+</h3>
+<p>{{this.subText}}</p>
 
 <section class="gh-content-entry-meta">
-    {{#if isPage}}
+    {{#if this.isPage}}
         <span class="gh-content-status-draft gh-badge gh-badge-black">Page</span>
     {{/if}}
 
-    {{#if isScheduled}}
+    {{#if this.isScheduled}}
         <span class="gh-content-status-draft gh-badge">Scheduled</span>
     {{/if}}
 
-    {{#if isDraft}}
+    {{#if this.isDraft}}
         <span class="gh-content-status-draft gh-badge gh-badge-red">Draft</span>
     {{/if}}
 
-    {{#if isFeatured}}
+    {{#if this.isFeatured}}
         <span class="gh-content-status-featured gh-badge gh-badge-blue">Featured</span>
     {{/if}}
 
-    {{#if (and isPublished (not post.page))}}
+    {{#if (and this.isPublished (not this.post.page))}}
         <span class="gh-content-status-published">Published</span>
     {{/if}}
 
-    by <span class="gh-content-entry-author">{{authorNames}}</span> &mdash;
+    by <span class="gh-content-entry-author">{{this.authorNames}}</span> &mdash;
 
-    {{#if isPublished}}
-        {{gh-format-post-time post.publishedAtUTC published=true}}
+    {{#if this.isPublished}}
+        {{gh-format-post-time this.post.publishedAtUTC published=true}}
     {{else if isScheduled}}
-        <span class="green">Will go live {{gh-format-post-time post.publishedAtUTC scheduled=true}}</span>
+        <span class="green">Will go live {{gh-format-post-time this.post.publishedAtUTC scheduled=true}}</span>
     {{else}}
-        Last edited {{gh-format-post-time post.updatedAtUTC draft=true}}
+        Last edited {{gh-format-post-time this.post.updatedAtUTC draft=true}}
     {{/if}}
 </section>