git-review: update documentation

Change-Id: I7d3b0d0e6c82d14ded8c75986c48fcb026b0f783
Reviewed-on: https://go-review.googlesource.com/1740
Reviewed-by: Russ Cox <rsc@golang.org>
2 files changed
tree: a5fae114fe6bd129be0c6c83f6c80d466b6fa5c0
  1. README
  2. git-review/