Add functionality to Stub to allow ConsecutiveCallStub

Add functionality to support ConsecutiveCallStub - PHPUnit via the Stub Class

- Useful for testing recursive functions

```php
<?php
    $user = Stub::make('User', array('getName' => Stub::consecutive('david', 'emma', 'sam', 'amy')));
    $user->getName(); //david
    $user->getName(); //emma
    $user->getName(); //sam
    $user->getName(); //amy
?>
```

http://phpunit.de/manual/3.6/en/test-doubles.html#test-doubles.stubs.examples.StubTest7.php