Move gh-pages branch files into /docs and add test files

- Jekyll ignore `/docs` and `/test` folders when using from root
- Update Staticman config to point to correct branch and data file location
- Replace `{{ base_path }}` references with `absolute_url` filter
- Update documentation

docs/_includes/comments-providers/discourse.html

@@ -0,0 +1,14 @@
+{% if site.comments.discourse.server %}
+{% include base_path %}
+{% capture canonical %}{{ base_path }}{% if site.permalink contains '.html' %}{{ page.url }}{% else %}{{ page.url | remove:'index.html' | strip_slash }}{% endif %}{% endcapture %}
+<script type="text/javascript">
+    DiscourseEmbed = { discourseUrl: '//{{ site.comments.discourse.server }}/',
+                       discourseEmbedUrl: '{{ canonical }}' };
+   (function () {
+     var d = document.createElement('script'); d.type = 'text/javascript'; d.async = true;
+     d.src = DiscourseEmbed.discourseUrl + 'javascripts/embed.js';
+     (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(d);
+   })();
+</script>
+<noscript>Please enable JavaScript to view the comments powered by [Discourse](http://forum.beta-europe.org/c/beta/website).</a></noscript>
+{% endif %}