This adds generic sort / sortRev functions for use in gmnhg templates
which use sort.Sort to sort anything that implements sort.Interface
(which includes lists of posts).
The existing sortPosts function that used to sort posts in reverse order
becomes an alias to sortRev for backwards compatibility.
gmnhg is the new program that generates a Gemini site from Hugo site
content. It reads its input from content/, static/, and layouts/gmnhg/.
Its output by default goes to output/.
More doc is available in the program doc header.
