Some cleaned up documentation, but no code changes.

Change-Id: I145398bb6d118c626ab3873ef75dbb64ebc286e9
Reviewed-on: https://go-review.googlesource.com/20404
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>