Feature / BC break: Simplify Collection by extending Response and merging Collector into ActionSender (#41 by @clue)

// old
$collector = new Collector($client);
$collector->coreShowChannels()->then(function (Collection $collection) {
    var_dump($collection->getResponse()->getFieldValue('Message'));
});

// new
$collector = new ActionSender($client);
$collector->coreShowChannels()->then(function (Collection $collection) {
    var_dump($collection->getFieldValue('Message'));
});

Feature / BC break: Replace deprecated SocketClient with new Socket component and improve forward compatibility with upcoming ReactPHP components (#39 by @clue)

Feature / BC break: Consistently require URL when creating client (#40 by @clue)