fix url when hosted in a github project project

I needed this for https://github.com/tyrcho/blog

Author: tyrcho

page/0archives.html

@@ -30,7 +30,7 @@ <h2 id="y{{ post.date | date: '%Y' }}">{{ post.date | date: '%Y' }}</h2>
                 <time>
                 {{ post.date | date:"%F" }} {{ post.date | date: "%a" }}.
                 </time>
-                <a class="title" href="{{ post.url }}">{{ post.title }}</a>
+                <a class="title" href="{{ post.url | prepend: site.baseurl }}">{{ post.title }}</a>
 
                 {% include category.html %}
                 {% include tag.html %}