Simplify usage by supporting new default loop

[clue]

This changeset simplifies usage by supporting the new default loop.

// old (still supported)
$proxy = new Clue\React\SshProxy\SshProcessConnector('[email protected]', $loop);
$proxy = new Clue\React\SshProxy\SshSocksConnector('[email protected]', $loop);

// new (using default loop)
$proxy = new Clue\React\SshProxy\SshProcessConnector('[email protected]');
$proxy = new Clue\React\SshProxy\SshSocksConnector('[email protected]');

Builds on top of reactphp/event-loop#226, reactphp/event-loop#229, reactphp/event-loop#232, reactphp/socket#260 and friends-of-reactphp/mysql#134