Support passing authentication as part of URI

[clue]

Quassel supports password-based authentication. If you want to create a "normal"
client connection, you're recommended to pass the authentication details as part
of the URI. You can pass the password h@llo URL-encoded (percent-encoded)
as part of the URI like this:

$factory->createClient('quassel://user:h%40llo@localhost')->then(
    function (Client $client) {
        // client sucessfully connected and authenticated
        $client->on('data', function ($data) {
            // next message to follow would be "SessionInit"
        });
    }
);

Note that if you do not pass the authentication details as part of the URI, then
this method will resolve with a "bare" Client right after connecting without
sending any application messages. This can be useful if you need full control
over the message flow, see the documentation for more details.

[clue]

Rebased on master now that #37 fixed the risky unit tests that caused PHPUnit to skip tests depending on this and thus leaving the Quassel core "unconfigured" during functional integration tests.