tutorial: update go_tutorial.txt should have been included in last CL; no idea why it was not
tutorial: update go_tutorial.txt
should have been included in last CL; no idea why it was not

R=brainman
CC=golang-dev
http://codereview.appspot.com/4005043
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go