Factory service test

[silvioq]

Hi, I hope this pull request was useful for you. I apologize for my basic English

  # test example ...
  $this->assertContainerBuilderHasCreatedByFactoryService(
      'target.service', 'factory.service', 'factoryMethod');

[silvioq]

Sadly, factories aren't compatible with Symfony 2.3 ... Do you plan remove BC for that version?

[Nyholm]

Could you also rebase on master?

[silvioq]

@Nyholm I'm sorry ... I'm doing some bad. How to I must rebase my PR?

[silvioq]

Hi @stloyd In December 2017 I reviewed the Symfony CS unmatches. I forgot something ?