compress/flate: use bytes.NewReader instead of NewBuffer in test
compress/flate: use bytes.NewReader instead of NewBuffer in test

Also, report allocations in benchmark.

R=golang-dev, r
CC=golang-dev
https://codereview.appspot.com/13410044

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