def file_size(path, rel = nil)
      return 0 if path.nil?
      path = path =~ /\// ? path : File.join('episodes', path)
      path = rel + path if rel
      File.size(path)
    end
def file_size(path, rel = nil)
      return 0 if path.nil?
      path = path =~ /\// ? path : File.join('episodes', path)
      path = rel + path if rel
      File.size(path)
    end
Returns the size of a given file in bytes. If there is just a filename
 without a path, this method assumes that the file is an episode audio file
 which lives in /episodes.

   {{ "example.m4a" | file_size }} => 4242