Test that fulfillment value of WritableStream.write() is undefined
Test that fulfillment value of WritableStream.close() is undefined
Ignore the return value of the sink's abort() function.
Clean up readable stream promise management.

- Spec change: removes unnecessary re-creation of [[waitPromise]].
- Reference implementation: clean up promise creation, resolving, and rejecting; uniformly clear the resolve/reject functions more consistently so as to detect bugs.
Fix test typos
Add acknowledgment for #202.
Use ws.foobar() style for tests about non static methods

See https://github.com/whatwg/streams/pull/197#issuecomment-54631762
Ignore the fulfillment value of the source's cancel().

Also, fix the type of ReadableStream.prototype.cancel() in the IDL to Promise<undefined>.
Remove an accent grave left by mistake
Use "sinkAbortPromise" also in the reference impl
Test that abort rejections from the sink are passed through
Use "fulfilled" in tests where appropriate over "resolved".

See https://github.com/domenic/promises-unwrapping/blob/master/docs/states-and-fates.md for the difference.
Fix the test calling readInto() when ReadableByteStream is waiting
Add cancel() method to ReadableByteStream