Add option to hide post (they're still build)

Fixes #9

exampleSite/content/about/index.md

@@ -1,6 +1,7 @@
 +++
 date = "2015-06-20T14:02:37+02:00"
 title = "About"
+hidden = true
 +++
 
 Lorem ipsum dolor sit amet, consectetur adipisicing elit. Ipsa ullam earum dolorum! Sed, perspiciatis.

layouts/partials/latest-posts.html

@@ -1,6 +1,6 @@
 <ul id="post-list" class="archive readmore">
     <h3>{{ with .Site.Params.readMore }}{{ . }}{{ else }}Read more{{ end }}</h3>
-    {{ range first 10 .Site.Pages }}
+    {{ range first 10 (where .Site.Pages "Params.hidden" "ne" "true") }}
     {{ $url := replace .Permalink .Site.BaseURL "" }}
         {{ if and (ne $url "about/") }}
         <li>

layouts/partials/post-list.html

@@ -1,5 +1,5 @@
 <ul id="post-list">
-    {{ range .Paginator.Pages }}
+    {{ range where .Paginator.Pages "Params.hidden" "ne" "true" }}
     {{ $url := replace .Permalink .Site.BaseURL "" }}
         {{ if ne $url "about/" }}
             <li>