shiny/example/goban: update for new paint model
shiny/example/goban: update for new paint model

Change-Id: Iaefb4ce6f590b1935f19c370513b8fb178daef80
Reviewed-on: https://go-review.googlesource.com/16900
Reviewed-by: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

golang/exp,AkihiroSuda/golang-exp-aspectgo,JamesDunne/exp,AkihiroSuda/golang-exp-aspectgo,JamesDunne/exp,golang/exp,golang/exp,AkihiroSuda/golang-exp-aspectgo