Update the source header to use Emacs library conventions

This patch contains no changes to the code logic.  Instead it updates
the header comment in the source to conform to the conventions
described in section D.8 of the Elisp Manual: “Conventional Headers
for Emacs Libraries.”

Signed-off-by: Eric James Michael Ritz <lobbyjones@gmail.com>
Add Jonas Bernoulli to the list of contributors