update hydrator with the new available interface/method in doctrine/common

There is a new interface in https://github.com/doctrine/common/pull/343, this is the implementation that will make possible to work with embeddables in DoctrineObject hydrator through this classmetadata implementation https://github.com/doctrine/doctrine2/pull/1185.

**This modification in composer.json is purposeful and will be removed as soon as/if doctrine/common PR gets merged w/ forced push. The objective is to make it possible to travis test the DoctrineModule with the new interface and show that this pr is dependent from a pr in doctrine/common**
@Ocramius maybe we don't need that reflection class anymore? since we can return the properties from the metadata?