Doesn't actually work for Node-core Stream objects in 0.8

[mixu]

... because in Node 0.8 core streams, there are no _read or _write methods:

[~] nvm use 0.8
Now using node v0.8.28
[~] node
> require('isStream').isWritable(require('fs').createWriteStream('/tmp/foo'))
false
> require('isStream').isReadable(require('fs').createReadStream('/tmp/foo'))
false
> require('isStream').isDuplex(new (require('net').Socket)())
false
>
(^C again to quit)
>

[~] nvm use 0.10
Now using node v0.10.32
[~] node
> require('isStream').isWritable(require('fs').createWriteStream('/tmp/foo'))
true
> require('isStream').isReadable(require('fs').createReadStream('/tmp/foo'))
true
> require('isStream').isDuplex(new (require('net').Socket)())
true
>
(^C again to quit)
>