Add note about authentication password in the doc

[atefBB]

Hi @dunglas.
When using password authentication while controlling TOR, the auth password must be generated using the command:
~> tor --hash-password "random_password"
which will generate a hashed password beginning with 16:DEE07A96.... (just an example).
So To control tor the php code must be :

$tc = new TorControl\TorControl(
                array(
                    'hostname'   => 'localhost',
                    'port'       => 9051,
                    'password'   => '16:DEE07A96A....',
                    // the generated password
                    'authmethod' => 1,
                )
            );

I think this trick must be mentioned in the README file.

[dunglas]

Would you mind opening a Pull Request?

[atefBB]

I'll do when I have TIME !

[atefBB]

I have been wrong about this issue! See details #14