Replace `ocramius/instantiator` with `doctrine/instantiator`.

Refs: Ocramius/Instantiator#13
should still be ``~1.0``, (or be ``~1.0, >= 1.0.1`` if you don't want to allow ``1.0.0``). Otherwise, you are requiring ``>= 1.0.1, < 1.1-dev``, preventing to get the next versions of the Instantiator