Add RecordArgumentsPromise which records the last arguments executed.

RecordArgumentsPromise can be used to record the last arguments provided to a promise.

```php
$prophecy = $this->prophesize('My\Class');
$prophecy
    ->doSomething(Prophecy\Argument::any())
    ->will($return = new RecordArgumentsPromise);
$prophecy->reveal()->doSomething('foo', 'bar');

// Called arguments are now available
$arguments = $return->getArguments();
```