Do not flatten the zip files downloaded via http

lib/cocoapods/downloader/http.rb

@@ -74,7 +74,8 @@ module Pod
           raise UnsupportedFileTypeError.new "Unsupported file type: #{type}"
         end
 
-        # If the archive only contained a folder, move its contents to the target (#727)
+        # If the archive is a tarball and it only contained a folder, move its contents to the target (#727)
+        if [:tgz, :tar, :tbz].include? type
           contents = target_path.children
           contents.delete(full_filename)
           entry = contents.first
@@ -82,6 +83,7 @@ module Pod
             FileUtils.move(entry.children, target_path)
           end
         end
+      end
 
     end
   end