wiki_pages/show: refactor post previews.

* Increase number of previews from 4 to 8.
* Eliminate wiki page post set classes.

app/logical/post_sets/wiki_page.rb

@@ -1,10 +0,0 @@
-module PostSets
-  class SearchError < StandardError
-  end
-
-  class WikiPage < PostSets::Post
-    def presenter
-      @presenter ||= ::PostSetPresenters::WikiPage.new(self)
-    end
-  end
-end

app/models/tag.rb

@@ -914,6 +914,10 @@ class Tag < ApplicationRecord
     return false
   end
 
+  def posts
+    Post.tag_match(name)
+  end
+
   include ApiMethods
   include CountMethods
   include CategoryMethods

app/models/wiki_page.rb

@@ -237,10 +237,6 @@ class WikiPage < ApplicationRecord
     self.dtext_links = DtextLink.new_from_dtext(body)
   end
 
-  def post_set
-    @post_set ||= PostSets::WikiPage.new(title, 1, 4)
-  end
-
   def presenter
     @presenter ||= WikiPagePresenter.new(self)
   end

app/presenters/post_set_presenters/wiki_page.rb

@@ -1,15 +0,0 @@
-module PostSetPresenters
-  class WikiPage < PostSetPresenters::Post
-    def posts
-      @post_set.posts
-    end
-
-    def post_previews_html(template)
-      result = super(template)
-      if result =~ /Nobody here but us chickens/
-        result = ""
-      end
-      result.html_safe
-    end
-  end
-end

app/views/wiki_pages/_posts.html.erb

@@ -1,7 +1,7 @@
 <% if wiki_page.tag.present? && wiki_page.tag.post_count > 0 %>
   <div id="wiki-page-posts">
-    <h2>Posts (<%= link_to "view all", posts_path(tags: wiki_page.title) %>)</h2>
+    <h2>Recent Posts <%= link_to "»", posts_path(tags: wiki_page.title) %></h2>
 
-    <%= wiki_page.post_set.presenter.post_previews_html(self) %>
+    <%= post_previews_html(wiki_page.tag.posts.limit(8), tags: wiki_page.title) %>
   </div>
 <% end %>