v0.4.0

• Feature / BC break: The Client implement DuplexStreamInterface and behaves like a normal stream
  (#21, #22 by @clue)

// old (custom "message" event)
$client->on('message', $callback);

// new (default "data" event)
$client->on('data', $callback);

// old (applies to app send*() methods
$client->sendClientInit(…);

// new (now uses write*() prefix)
$client->writeClientInit(…);

// shared interfaces allow for interoperability with other components
$client->pipe($logger);

// allows advanced / custom messages through writable interface
$client->write(array(…));

// supports and reports back pressure to avoid buffer overflows
$more = $client->write*(…);
$client->pause();
$client->resume();

• Feature: Use default time zone and support sub-second accuracy for heartbeats
  (#20 by @clue)