doc/roadmap: put "App Engine support" under "Done".
doc/roadmap: put "App Engine support" under "Done".

R=rsc, dsymonds
CC=golang-dev
http://codereview.appspot.com/4528053
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go