2.0.0 Beta 2

• Removed the optional $bytes parameter from WritableStream::end().
• ReadableResourceStream::read() now performs a read immediately on the stream to avoid leaving data in PHP's internal stream buffers.
• Renamed $length param on ReadableResourceStream::read() to $limit to better reflect its purpose.
• Added a $limit param to Amp\ByteStream\buffer() and Payload::buffer() to set a limit on the maximum bytes that can be buffered.