Also updates the package description.

Change-Id: I782a9d34d5a35aff92873efc6d511f95686cd5d6
Reviewed-on: https://go-review.googlesource.com/35071
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Matt Layher <mdlayher@gmail.com>