A+C: add Steve Newman (Google CLA)

Steve Newman (Google CLA) was missing from the CONTRIBUTORS file,
presumably because his old commits (made prior to Go being open
source) in SVN/perforce were imported into hg/git later as
"devnull@localhost", which probably didn't match anything, and we
didn't start tracking CLA contributions prior to the Go
open source release.

As a fun historical note, the initial HTTP client from Steve:
https://github.com/golang/go/commit/f315fb3

Change-Id: I2b8da4564d99820504788ecc41495a62391078d5
Reviewed-on: https://go-review.googlesource.com/16864Reviewed-by: Ian Lance Taylor <iant@golang.org>

CONTRIBUTORS

@@ -780,6 +780,7 @@ Stephen Ma <stephenm@golang.org>
 Stephen McQuay <stephen@mcquay.me>
 Stephen Weinberg <stephen@q5comm.com>
 Steve McCoy <mccoyst@gmail.com>
+Steve Newman <snewman@google.com>
 Steve Phillips <elimisteve@gmail.com>
 Steve Streeting <steve@stevestreeting.com>
 Steven Elliot Harris <seharris@gmail.com>