Depend on our own ncursesw fork

The fork of ncursesw is [here](https://github.com/sup-heliotrope/ncursesw-ruby). I'd really like to make the [gem](https://rubygems.org/gems/ncursesw-sup) owned by all maintainers of sup. But I had no luck finding where to set ownership :(

Currently it works well on my Ubuntu 12.04 VM w/ Ruby 1.8. I'll cook up a wiki page on how to install sup via rubygems on Ubuntu 12.04 (and 13.04 later).