Feature: Add new SocketServer and deprecate Server to avoid class name collisions. (#263 by @clue)

The new SocketServer class has been added with an improved constructor signature as a replacement for the previous Server class in order to avoid any ambiguities. The previous name has been deprecated and should not be used anymore. In its most basic form, the deprecated Server can now be considered an alias for new SocketServer.

// deprecated
$socket = new React\Socket\Server(0);
$socket = new React\Socket\Server('127.0.0.1:8000');
$socket = new React\Socket\Server('127.0.0.1:8000', null, $context);
$socket = new React\Socket\Server('127.0.0.1:8000', $loop, $context);

// new
$socket = new React\Socket\SocketServer('127.0.0.1:0');
$socket = new React\Socket\SocketServer('127.0.0.1:8000');
$socket = new React\Socket\SocketServer('127.0.0.1:8000', $context);
$socket = new React\Socket\SocketServer('127.0.0.1:8000', $context, $loop);

Feature: Update Connector signature to take optional $context as first argument. (#264 by @clue)

The new signature has been added to match the new SocketServer and consistently move the now commonly unneeded loop argument to the last argument. The previous signature has been deprecated and should not be used anymore. In its most basic form, both signatures are compatible.

 // deprecated
$connector = new React\Socket\Connector(null, $context);
$connector = new React\Socket\Connector($loop, $context);

// new
$connector = new React\Socket\Connector($context);
$connector = new React\Socket\Connector($context, $loop);