* Use height=0 and width=0 for automatic size everywhere? Well, it seems to
  work with recent versions of dialog (yay!), but changing the default values
  for 'width' and 'height' in pythondialog widgets would break backward
  compatibility. -> major version bump? API versioning?

* Support for --output-separator.

* Maybe get rid of _create_temporary_directory() in favor of what Python has
  in its stdlib now?

* Try detecting the terminal window size in order to make reasonable height
  and width defaults. Hmmm---should also then check for terminal resizing...

* Support --tailboxbg
