suzerain: properly error on nargs < 2

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44364 0bd85f0b-c151-43b9-a1e9-27231104551f
suzerain: #3076 add summary_surf.py

git-svn-id: https://svn.ices.utexas.edu/repos/pecos/suzerain/trunk@44365 0bd85f0b-c151-43b9-a1e9-27231104551f