posts: fix incorrect large_file_url for animated_gifs.

For animated_gif posts, large_file_url was returning
"/data/sample-$md5.jpg" instead of "/data/$md5.gif".

app/logical/storage_manager.rb

@@ -56,7 +56,7 @@ class StorageManager
     elsif type == :large && post.has_large?
       "#{base_url}/sample/#{subdir}#{seo_tags(post)}#{file}"
     else
-      "#{base_url}/#{subdir}#{seo_tags(post)}#{file}"
+      "#{base_url}/#{subdir}#{seo_tags(post)}#{post.md5}.#{post.file_ext}"
     end
   end
 

test/unit/post_test.rb

@@ -2653,6 +2653,16 @@ class PostTest < ActiveSupport::TestCase
     end
   end
 
+  context "URLs:" do
+    should "generate the correct urls for animated gifs" do
+      @post = FactoryGirl.build(:post, md5: "deadbeef", file_ext: "gif", tag_string: "animated_gif")
+
+      assert_equal("http://localhost/data/preview/deadbeef.jpg", @post.preview_file_url)
+      assert_equal("http://localhost/data/deadbeef.gif", @post.large_file_url)
+      assert_equal("http://localhost/data/deadbeef.gif", @post.file_url)
+    end
+  end
+
   context "Mass assignment: " do
     should_not allow_mass_assignment_of(:last_noted_at).as(:member)
   end