blog: new post "Errors are values"

I won't submit it this time. Sorry.

Change-Id: I3a63985bf6b12a22d0371f8fdf5c0fcd2a01ff8b
Reviewed-on: https://go-review.googlesource.com/2539
Reviewed-by: Andrew Gerrand <adg@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
1 file changed