Add includes for static-based comments powered by Staticman

- Configure Staticman with sane defaults
- Build comment form to capture new comments and ajax data to Staticman
- Build comments view that iterates over `_data/comments/post-slug/*.yml` files

_includes/comments-providers/scripts.html

@@ -9,6 +9,8 @@
   {% include /comments-providers/facebook.html %}
 {% when "google-plus" %}
   {% include /comments-providers/google-plus.html %}
+{% when "staticman" %}
+  {% include /comments-providers/staticman.html %}
 {% when "custom" %}
   {% include /comments-providers/custom.html %}
 {% endcase %}