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/_layouts/archive.html

@@ -0,0 +1,24 @@
+---
+layout: default
+---
+
+{% if page.header.overlay_color or page.header.overlay_image or page.header.image %}
+  {% include page__hero.html %}
+{% endif %}
+
+{% if page.url != "/" and site.breadcrumbs %}
+  {% unless paginator %}
+    {% include breadcrumbs.html %}
+  {% endunless %}
+{% endif %}
+
+<div id="main" role="main">
+  {% include sidebar.html %}
+
+  <div class="archive">
+    {% unless page.header.overlay_color or page.header.overlay_image %}
+      <h1 class="page__title">{{ page.title }}</h1>
+    {% endunless %}
+    {{ content }}
+  </div>
+</div>