html/template: fix typo and make grammar consistent in comments.
html/template: fix typo and make grammar consistent in comments.

R=golang-dev, r
CC=golang-dev
http://codereview.appspot.com/5866044
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go