Update post-grid.html

Removed need for a post teaser

_includes/post-grid.html

@@ -1,6 +1,6 @@
 <article class="tile" itemscope itemtype="http://schema.org/Article">
   <a href="{{ site.url }}{{ post.url }}" title="{{ post.title }}" class="post-teaser">{% if post.image.teaser %}<img src="{{ site.url }}/images/{{ post.image.teaser }}" alt="teaser" itemprop="image">
-    {% else %}<img src="{{ site.url }}/images/{{ site.teaser }}" alt="teaser" itemprop="image">{% endif %}</a>
+    {% elsif site.teaser %}<img src="{{ site.url }}/images/{{ site.teaser }}" alt="teaser" itemprop="image">{% endif %}</a>
   {% if post.date %}<p class="entry-date date published"><time datetime="{{ post.date | date: "%Y-%m-%d" }}" itemprop="datePublished">{{ post.date | date: "%B %d, %Y" }}</time></p>{% endif %}
   <h2 class="post-title" itemprop="name"><a href="{{ site.url }}{{ post.url }}">{{ post.title }}</a></h2>
   <p class="post-excerpt" itemprop="description">{{ post.excerpt | strip_html | truncate: 160 }}</p>