gofmt-xx.slide: present slides for GopherChina talk on gofmt

gofmt-en.slide:	English version
gofmt-cn.slide: Mandarin version

Change-Id: Id406b24dff2e3354c7e3cf9df7b723342cd2658a
Reviewed-on: https://go-review.googlesource.com/9972
Reviewed-by: Rob Pike <r@golang.org>