bdowns: add bdowns/main.go for GopherCon
bdowns: add bdowns/main.go for GopherCon

Change-Id: I8552363d935bed38e7c08d6ef5c144bcbd721152
Reviewed-on: https://go-review.googlesource.com/48779
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/scratch