Release 0.1.0 Beta

First beta release:
* Offers `ResourceMapper` to define new resources.
* Allows for before and after callbacks.
* Implements a Doctrine2 driver.
* 100% code coverage + integration tests.

See the [`README.md`](https://github.com/Tuxion/DoctrineRest/tree/release/0.1.0-beta#readme) file for more details.
These abstract methods are already implemented by DriverInterface. Why redefine them?