switch post previews to use flexbox, add better styling for cropped thumbnails

app/presenters/post_set_presenters/base.rb

@@ -12,7 +12,7 @@ module PostSetPresenters
       end
 
       posts.each do |post|
-        html << PostPresenter.preview(post, options.merge(:show_cropped => true, :tags => @post_set.tag_string, :raw => @post_set.raw))
+        html << PostPresenter.preview(post, options.merge(:tags => @post_set.tag_string, :raw => @post_set.raw))
         html << "\n"
       end
 

app/presenters/post_set_presenters/post.rb

@@ -11,6 +11,10 @@ module PostSetPresenters
       @tag_set_presenter ||= TagSetPresenter.new(related_tags)
     end
 
+    def post_previews_html(template, options = {})
+      super(template, options.merge(show_cropped: true))
+    end
+
     def related_tags
       if post_set.is_pattern_search?
         pattern_tags