add support for download files

app/models/post.rb

@@ -102,7 +102,7 @@ class Post < ActiveRecord::Base
     end
 
     def preview_file_url
-      if is_flash?
+      if !is_image?
         return "/images/download-preview.png"
       end
       

app/presenters/post_presenter.rb

@@ -66,6 +66,8 @@ class PostPresenter < Presenter
     
     if @post.is_flash?
       template.render("posts/partials/show/flash", :post => @post)
+    elsif !@post.is_image?
+      template.render("posts/partials/show/download", :post => @post)
     elsif @post.is_image?
       template.render("posts/partials/show/image", :post => @post)
     end

app/views/posts/partials/show/_download.html.erb

@@ -0,0 +1 @@
+<p><%= link_to "Save this file (right click and save)", post.file_url %></p>