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/scripts.html

@@ -0,0 +1,4 @@
+<script src="{{ '/assets/js/main.min.js' | absolute_url }}"></script>
+
+{% include analytics.html %}
+{% include /comments-providers/scripts.html %}