Comments toggeled per-page and add default setting

Comments toggeled per-page by setting "comments = true" or "comments =
false" in front matter. If not set, will use new default setting defined
in config.toml.

exampleSite/config.toml

@@ -14,6 +14,7 @@ pygmentCodeFences = true
   dateFormat = "January 2, 2006"
   commit = false
   rss = true
+  comments = true
 
 [Author]
   name = "Some Person"

exampleSite/content/page/about.md

@@ -1,6 +1,7 @@
 ---
 title: About me
 subtitle: Why you'd want to go on a date with me
+comments: false
 ---
 
 My name is Inigo Montoya. I have the following qualities:

layouts/partials/disqus.html

@@ -1,5 +1,7 @@
-{{ if .Site.DisqusShortname }}
+{{ if (.Params.comments) | or (and (not (isset .Params "comments")) (.Site.Params.comments)) }}
+  {{ if .Site.DisqusShortname }}
     <div class="comments">
       {{ template "_internal/disqus.html" . }}
     </div>
+  {{ end }}
 {{ end }}

layouts/partials/page.html

@@ -2,11 +2,13 @@
   <div class="row">
     <div class="col-lg-8 col-lg-offset-2 col-md-10 col-md-offset-1">
       {{ .Content }}
+      {{ if (.Params.comments) | or (and (not (isset .Params "comments")) (.Site.Params.comments)) }}
         {{ if .Site.DisqusShortname }}
           <div class="disqus-comments">
             {{ template "_internal/disqus.html" . }}
           </div>
         {{ end }}
+      {{ end }}
     </div>
   </div>
 </div>

layouts/partials/post.html

@@ -18,11 +18,13 @@
         {{ end }}
       </ul>
 
+      {{ if (.Params.comments) | or (and (not (isset .Params "comments")) (.Site.Params.comments)) }}
         {{ if .Site.DisqusShortname }}
           <div class="disqus-comments">
             {{ template "_internal/disqus.html" . }}
           </div>
         {{ end }}
+      {{ end }}
 
     </div>
   </div>