Fix linking to tags that contain a space in their name. (#81)

Jekyll allows you to specify tags as both a space-delimited string
and an array of tags. If an array of tags is used then tags can
contain spaces.

This commit fixes jekyll-dash to correctly link to tag pages for
tags which have a space in their name.

Author: SadieCat

_layouts/home.html

@@ -17,7 +17,7 @@ <h1>recent articles</h1>
             {% if site.plugins contains "jekyll/tagging" %}
             <div class="post-tags">
                 {% for tag in post.tags %}
-                <a class="tag" href="/tag/{{ tag }}/">{{ tag }}</a>
+                <a class="tag" href="{{ tag | tag_url }}">{{ tag }}</a>
                 {% endfor %}
             </div>
             {% endif %}

_layouts/post.html

@@ -9,7 +9,7 @@ <h1 class="post-title">{{ page.title }}</h1>
   {% if site.plugins contains "jekyll/tagging" %}
   <div class="post-tags">
       {% for tag in page.tags %}
-      <a class="tag" href="/tag/{{ tag }}/">{{ tag }}</a>
+      <a class="tag" href="{{ tag | tag_url }}">{{ tag }}</a>
       {% endfor %}
   </div>
   {% endif %}

_layouts/tag_page.html

@@ -17,7 +17,7 @@ <h1 class="post-title">articles tagged with <a class="tag" href="/tag/{{ page.ta
 
           <div class="post-tags">
               {% for tag in post.tags %}
-              <a class="tag" href="/tag/{{ tag }}/">{{ tag }}</a>
+              <a class="tag" href="{{ tag | tag_url }}">{{ tag }}</a>
               {% endfor %}
           </div>
           {% if site.dash.date_format %}