Update StrategyInterface.php

This PR is to implement functionality as detailed in the AbstractHydrator. This should *not* be a BC break.

https://github.com/zendframework/zf2/blob/master/library/Zend/Stdlib/Hydrator/AbstractHydrator.php#L114
https://github.com/zendframework/zf2/blob/master/library/Zend/Stdlib/Hydrator/AbstractHydrator.php#L131
Update StrategyInterface.php
Update StrategyInterface.php

Added todo for version 3.0.
Merge pull request #4539 from spiffyjr/patch-2

Update StrategyInterface.php
Merge branch 'hotfix/4539'

Close #4539