fix prefix in streams by using a streams2 transform.

[juliangruber]

fixes #42

deps are bigger but it's less hacky / likely to break and fixes the tests in node 0.8

[dominictarr]

I think there is a better way to fix this,
if you just use on('data' as well as wrap read.
I think it currently checks for .read and wraps that,
but if it's not there it assigns a data listener.
One simple way would be to wrap emit and if it's emit('data',...) then fix the key.

[juliangruber]

But what was the problem on 0.8 then?

[dominictarr]

it's about the changing ways that readable-stream's classic streams polyfil worked.

if it's a non-core (ie, from the isaacs/readables-stream) in 0.8 then it works a different way to what it works now.