fix buttons in the header

Author: ulysses4ever

_layouts/default.html

@@ -13,7 +13,7 @@
     <section class="page-header gibbon-header-img">
       <h1 class="project-name">{{ site.title | default: site.github.repository_name }}</h1>
       <h2 class="project-tagline">{{ site.description | default: site.github.project_tagline }}</h2>
-      {% if site.github.is_project_page %}
+      {% if site.github.is_user_page %}
         <a href="{{ site.github.repository_url }}" class="btn">View on GitHub</a>
         <a href="{{ site.baseurl }}/haddocks/" class="btn">API documentation</a>
       {% endif %}