Add Fluid where filter, fix slug (#47)

- Fix issue with path base and logon redirects

src/default-theme/single-post.liquid

@@ -2,8 +2,8 @@
 <h1>{{ post.title }}</h1>
 <h4 class="item-meta text-muted">
   {% if post.published_on -%}
-    Published {{ post.published_on | date: "dddd, MMMM d, yyyy" }}
-    at {{ post.published_on | date: "h:mm tt" | downcase }}
+    Published {{ post.published_on | format_date: "dddd, MMMM d, yyyy" }}
+    at {{ post.published_on | format_date: "h:mm tt" | downcase }}
   {%- else -%}
     **DRAFT**
   {% endif %}