Faker integration

I made the AttributeReplacer configurable and wrote a Faker implementation for it, including tests. Also added a method to quickly enable this implementation and updated the [readme](https://github.com/JeroenNoten/TestDummy/blob/a2c29582b1ce051e96c8063c8d7633ccd72410e1/readme.md#enable-faker-integration).

Hope you like it.