bytes: document that Buffer.Write grows the buffer Do a little reformatting too. Fixes issue 5152.
bytes: document that Buffer.Write grows the buffer
Do a little reformatting too.
Fixes issue 5152.

R=golang-dev, bradfitz, gri
CC=golang-dev
https://codereview.appspot.com/8157044

apparentlymart/golang,gnanderson/go,pombredanne/go-deleteme,tv42/old-go,gnanderson/go,gnanderson/go,dsriram/golang,dsriram/golang,tv42/old-go,gnanderson/go,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,gnanderson/go,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,pombredanne/go-deleteme,apparentlymart/golang,gnanderson/go,apparentlymart/golang,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,dsriram/golang,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,gnanderson/go,apparentlymart/golang,apparentlymart/golang,pombredanne/go-deleteme