Protocol\Smtp: toggle QUIT>221 command at disconnect

[Slamdunk]

Original issue: #27

When a SMTP server implements a timeout, a script like this is a pain in the ass:

$transport = new Zend\Mail\Transport\Smtp();

$message = new Zend\Mail\Message();
$message->setFrom('test@test.com');
$message->addTo('test@test.com');
$message->setSubject('Test ' . date('H:i:s'));
$message->setBody('Test ' . date('H:i:s'));

$transport->send($message);
var_dump('E-mail sent');

sleep(305);

var_dump('Soon to exit...');
exit;

// E-mail sent
// Soon to exit...
// Notice: fwrite(): send of 6 bytes failed with errno=32 Broken pipe in ./zend-mail/src/Protocol/AbstractProtocol.php on line 255
// Fatal error: Uncaught Zend\Mail\Protocol\Exception\RuntimeException: Could not read from 127.0.0.1 in ./zend-mail/src/Protocol/AbstractProtocol.php:301

While the other features mentioned in #27 can be implemented in a custom way using OOP, this one cannot.

If a user wants to use Protocol\Smtp and Protocol\Smtp\Auth\Login, the fact that:

1. quit() is hardcoded into Protocol\Smtp::_disconnect()
2. Protocol\Smtp::_disconnect() is hardcoded into Protocol\AbstractProtocol::__destruct()

Makes impossible to customize zendframework/zend-mail component, even with subclassing, without rewriting the core code lines of Zend\Protocol\*

With this PR a user can decide wether or not send the QUIT at __destruct / exit:

$transport = new Zend\Mail\Transport\Smtp(new Zend\Mail\Transport\SmtpOptions(array(
    'connection_class'  => 'smtp', // or plain, login, crammd5
    'connection_config' => [
        'use_complete_quit' => false,
    ],
)));

As soon as the PR is accepted, I'll PR to the doc.

[Slamdunk]

@Maks3w does the change sound applicable this way?

[Slamdunk]

Ping anyone?

[weierophinney]

This looks good. I'll merge to develop for release with 2.8.0 (which will likely be a couple weeks, as there are a few other pending items that I'm waiting for author feedback on). I'll take care of the conflict during merge.

[weierophinney]

Merged to develop for release with 2.8.0.

[Slamdunk]

Here the doc against develop: #131