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

_config.yml

@@ -30,12 +30,12 @@ comments:
     colorscheme          : # "light" (default), "dark"
 staticman:
   allowedFields          : ['name', 'email', 'url', 'message']
-  branch                 : # "master", "gh-pages"
+  branch                 : "master"
   commitMessage          : "New comment."
   filename               : comment-{@timestamp}
   format                 : "yml"
   moderation             : true
-  path                   : "_data/comments/{options.slug}"
+  path                   : "docs/_data/comments/{options.slug}"
   requiredFields         : ['name', 'email', 'message']
   transforms:
     email                : "md5"
@@ -135,6 +135,8 @@ exclude:
   - Rakefile
   - README
   - tmp
+  - /docs # ignore Minimal Mistakes /docs
+  - /test # ignore Minimal Mistakes /test
 keep_files:
   - .git
   - .svn