content: add Go 1.8 release announcement post

Change-Id: I2f12ee603571dd3d253907b836ff264c57d95fe7
Reviewed-on: https://go-review.googlesource.com/37133
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed