[Node] Updating stream interfaces and removing redundant interfaces.

We duplicated the EventEmitter and Stream interfaces in the "event" module, so I removed the redundant interface definitions.

I have updated the ReadableStream/WritableStream interfaces in accordance with the current documentation:
http://nodejs.org/api/stream.html

I added class definitions for Writable/Transform/Duplex/PassThrough in 'event'. These classes are described in the following Node documentation:
http://nodejs.org/api/stream.html#stream_api_for_stream_implementors

I realize the diff looks large, but that's because we referenced the redundant interface all over the typings. Let me know if you have any questions.