Return error from WriteByte, to match bufio.Writer.
Return error from WriteByte, to match bufio.Writer.

R=gri
DELTA=4  (1 added, 0 deleted, 3 changed)
OCL=28868
CL=28899
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go