talksapp: use Go 1.9, update bot.html URLs

Go 1.8 isn't supported anymore by goapp test (which is run by Travis CI).

Also add deploy command to README.

Change-Id: I90ee9a699fd95c74ce51446dbc35533738c05eea
GitHub-Last-Rev: af88a3b3ebd4c71b0ae48014b41db909db4d2f1e
GitHub-Pull-Request: golang/gddo#590
Reviewed-on: https://go-review.googlesource.com/c/150059
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>