Updated to latest revision in urbit git master, fixes build error caused by missing sources.
Updated description and website.
Fixed date/version format to ISO 8061.
This reverts commit f61176c5396ed513f3d399f73f38ab78a066667f, reversing
changes made to a27ca029ee2b39e04d7d2a516a7228f4b62067fb.
Conflicts:
pkgs/development/libraries/ncurses/default.nix