content/toward-go2: add "Future of Go" talk, Gophercon 2017

Change-Id: I0f62b3ffb60b026f9f1b0bf745afc830711a3c48
Reviewed-on: https://go-review.googlesource.com/48371
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
20 files changed