doc/gopher: add a small gif to use as an app engine logo on GAE pages.
doc/gopher: add a small gif to use as an app engine logo on GAE pages.

R=golang-dev, dsymonds
CC=golang-dev
http://codereview.appspot.com/4591078
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go