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/_sass/vendor/font-awesome/_fixed-width.scss

@@ -0,0 +1,6 @@
+// Fixed Width Icons
+// -------------------------
+.#{$fa-css-prefix}-fw {
+  width: (18em / 14);
+  text-align: center;
+}