v0.5.0

• Feature / BC break: Consistent end event semantics (EOF)
  (#70 by @clue)

  The end event will now only be emitted for a successful end, not if the
  stream closes due to an unrecoverable error event or if you call close()
  explicitly.
  If you want to detect when the stream closes (terminates), use the close
  event instead.

• BC break: Remove custom (undocumented) full-drain event from Buffer
  (#63 and #68 by @clue)

  The full-drain event was undocumented and mostly used internally.
  Relying on this event has attracted some low-quality code in the past, so
  we've removed this from the public API in order to work out a better
  solution instead.
  If you want to detect when the buffer finishes flushing data to the stream,
  you may want to look into its end() method or the close event instead.

• Feature / BC break: Consistent event semantics and documentation,
  explicitly state when events will be emitted and which arguments they
  receive.
  (#73 and #69 by @clue)

  The documentation now explicitly defines each event and its arguments.
  Custom events and event arguments are still supported.
  Most notably, all defined events only receive inherently required event
  arguments and no longer transmit the instance they are emitted on for
  consistency and performance reasons.

  // old (inconsistent and not supported by all implementations)
  $stream->on('data', function ($data, $stream) {
      // process $data
  });
  
  // new (consistent throughout the whole ecosystem)
  $stream->on('data', function ($data) use ($stream) {
      // process $data
  });

  This mostly adds documentation (and thus some stricter, consistent
  definitions) for the existing behavior, it does NOT define any major
  changes otherwise.
  Most existing code should be compatible with these changes, unless
  it relied on some undocumented/unintended semantics.

• Feature / BC break: Consistent method semantics and documentation
  (#72 by @clue)

  This mostly adds documentation (and thus some stricter, consistent
  definitions) for the existing behavior, it does NOT define any major
  changes otherwise.
  Most existing code should be compatible with these changes, unless
  it relied on some undocumented/unintended semantics.

• Feature: Consistent pipe() semantics for closed and closing streams
  (#71 from @clue)

  The source stream will now always be paused via pause() when the
  destination stream closes. Also, properly stop piping if the source
  stream closes and remove all event forwarding.

• Improve test suite by adding PHPUnit to require-dev and improving coverage.
  (#74 and #75 by @clue, #66 by @nawarian)