Feature: Apply protocol version and username/password auth from SOCKS URI (#43 by @clue)

// explicitly use SOCKS5
$client = new Client('socks5://127.0.0.1', $loop);

// use authentication (automatically SOCKS5)
$client = new Client('user:pass@127.0.0.1', $loop);

More explicit client examples, including proxy chaining (#42 by @clue)