I've also inferred extra information through examining the source code, as particular options are not well-documented.
This also updates envify's typings to be more specific.
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
As a result of these changes, I needed to slightly alter other typings to refer to the new interface name. This was unavoidable; I had to rename the `EventEmitter` interface to `NodeEventEmitter` to avoid clashing with the `events.EventEmitter` class that implements `NodeEventEmitter`.
