go.talks: add support for mouse wheel interaction on the slides.
go.talks: add support for mouse wheel interaction on the slides.

R=adg
CC=golang-dev
https://golang.org/cl/11967047

Karthikvb/talks,Karthikvb/talks,Karthikvb/talks,Karthikvb/talks,Karthikvb/talks,Karthikvb/talks