I thought it would be nice to have a man page for this wonderful piece of software, especially with it being available in various package managers like Homebrew.
This man page is basically a reformatting (and slight reorganizing to fit the typical man page structure) of the official docs.
src/manpage.md is the Markdown source which can generate the actual man page (share/man/man1/minisign.1) using ronn <http://rtomayko.github.com/ronn/>
Update: Corrected a few typos that I didn't catch before original submission.