container/list: add package example
container/list: add package example

R=golang-dev, minux.ma
CC=golang-dev
https://codereview.appspot.com/7306078

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