Unify local links to posts (#65).

_includes/panel.html

@@ -27,7 +27,7 @@
         {% assign post = site.posts | where: "url", post_url | first %}
 
         {% if post %}
-          {% assign url = post.url | prepend: site.baseurl %}
+          {% assign url = post.url | relative_url %}
 
           <li><a href="{{ url }}">{{ post.title }}</a></li>
 

_includes/sidebar.html

@@ -21,7 +21,7 @@
 
     <div class="profile-text mt-3">
       <div id="site-title">
-        <a href="{{ site.baseurl }}/">{{- site.title -}}</a>
+        <a href="{{ '/' | relative_url }}">{{- site.title -}}</a>
       </div>
       <div id="site-subtitle" class="font-italic">{{- site.tagline -}}</div>
     </div>