node bug fix, make ReadableStream the same as stream.ReadableStream

This simply applies the same change to RedableStream that was made to stream.ReadableStream in: https://github.com/borisyankov/DefinitelyTyped/commit/d0139df89deb691b3a25506e942d41707c8afce8

It avoids this error:
![node_pipe](https://f.cloud.github.com/assets/80104/1609664/88770380-5551-11e3-9cb1-9e33d0bb130b.png)