2017-03-24: fix: cannot make plot-skip 0

fix: cannot make plot-skip 0

diff --git a/examples/benchmark.w b/examples/benchmark.w
--- a/examples/benchmark.w
+++ b/examples/benchmark.w
@@ -229,7 +229,7 @@ define : flatten li
 define* : plot-benchmark-result bench H #:key filename
      let*
         : ensemble-member-count 128
-          ensemble-member-plot-skip 0
+          ensemble-member-plot-skip 1 ;; must not be zero!
           y_0 : apply min : map car : map cdr bench
           y_m : apply max : map car : map cdr bench
           nb : apply max : interleave (map car (map car bench)) (map car (map cdr (map car bench)))