Nested functions are the devil, especially ones that
use variables from the outer scope. Refactoring
_download_name to use a helper class helps make
the scoping more explicit and will undoubtably
prevent bugs in the future.
I think this makes _download_name drastically more readable.
Also cleaned up some duplicated code and
made download_directory respect the passed in parameter
instead of being the default.
a15d7ca543