text: Title: Document how to use Faker inside LazyAttribute
  Body: #### The problem
  The class `factory.Faker` is a wrapper around the "real" Faker.
  It works fine but sometimes you need to use it inside a LazyAttribute and you need to generate a value.
  
  At the moment I use a trick like
  ```python
  class MyFactory(factory.Factory):
      class Params:
          user = None
  
      @factory.lazy_attribute
      def current_ip_address(obj):
          if obj.user:
              return obj.user.ip_address
          else:
              return factory.Faker('ipv4').evaluate(None, None, {'locale': factory.Faker._DEFAULT_LOCALE})
  ```
  
  #### Proposed solution
  In some cases I can use `Maybe` but not always.
  Would be nice to have a section in the documentation that explain how to use `Faker` in `LazyAttribute`
  
  