License as BSD-2, copyright the authors $(git shortlog -s)

BSD-2 is slightly more permissive than the CMake license which includes
the endorsement clause.  The Git history is a better statement of
authorship than copyright notices in files.  If employers would assert
copyright, those assertions can be listed in a table.

Signed-off-by: Jed Brown <jed@59A2.org>
Signed-off-by: John Fettig <john.fettig@gmail.com>
Signed-off-by: Constantine Khroulev <ckhroulev@alaska.edu>