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/_posts/2012-01-02-layout-related-posts.md

@@ -0,0 +1,12 @@
+---
+title: "Layout: Related Posts Enabled"
+related: true
+categories:
+  - Layout
+  - Uncategorized
+tags:
+  - related posts
+  - layout
+---
+
+This post has related posts enabled.