2016-06-03: reduce number of ensemble members to 40, because that’s what guile

reduce number of ensemble members to 40, because that’s what guile 2.0.11 can handle

diff --git a/examples/ensemble-estimation.w b/examples/ensemble-estimation.w
--- a/examples/ensemble-estimation.w
+++ b/examples/ensemble-estimation.w
@@ -209,7 +209,7 @@ Limitations: y is a single value. R and 
 
 define : main args
     let*
-      : optimized : EnSRT H x^b P y⁰ R y⁰-pos 100
+      : optimized : EnSRT H x^b P y⁰ R y⁰-pos 40
         x-opt : list-ref optimized 0
         x-deviations : list-ref optimized 1
         ; std : sqrt : * {1 / {(length x-deviations) - 1}} : sum-ec (: i x-deviations) : expt i 2