Add support for customizable date format (daattali#533)

* Add support for customizable date format

* Add support for customizable date format

Author: bangjunyoung

_config.yml

@@ -150,6 +150,9 @@ excerpt_length: 50
 # and RSS feed title
 title-separator: "-"
 
+# Ruby Date Format
+date_format: "%B %-d, %Y"
+
 # --- Don't need to touch anything below here (but you can if you want) --- #
 
 # Output options (more information on Jekyll's site)

_includes/header.html

@@ -36,7 +36,7 @@ <h2 class="{{ include.type }}-subheading">{{ page.subtitle }}</h2>
 		  {% endif %}
 
 		  {% if include.type == "post" %}
-		  <span class="post-meta">Posted on {{ page.date | date: "%B %-d, %Y" }}</span>
+		  <span class="post-meta">Posted on {{ page.date | date: site.date_format }}</span>
 		  {% endif %}
         </div>
       </div>
@@ -61,7 +61,7 @@ <h2 class="{{ include.type }}-subheading">{{ page.subtitle }}</h2>
 		  {% endif %}
 
 		  {% if include.type == "post" %}
-		  <span class="post-meta">Posted on {{ page.date | date: "%B %-d, %Y" }}</span>
+		  <span class="post-meta">Posted on {{ page.date | date: site.date_format }}</span>
 		  {% endif %}
         </div>
       </div>

tags.html

@@ -25,7 +25,7 @@ <h2 id="{{- tag -}}" class="linked-section">
             <div class="tag-entry">
                 <a href="{{ post.url | relative_url }}">{{- post.title -}}</a>
                 <div class="entry-date">
-                    <time datetime="{{- post.date | date_to_xmlschema -}}">{{- post.date | date: "%B %d, %Y" -}}</time>
+                    <time datetime="{{- post.date | date_to_xmlschema -}}">{{- post.date | date: site.date_format -}}</time>
                 </div>
             </div>
         {%- endfor -%}