Don't build debug strings when factory debug: false

[thetamind]

This commit adds earlier debug: true checks so log_value/5 and debug/2 avoid building messages only to be discarded later.

I was profiling my tests and saw building debug strings took up a bit of the time building factory values.

  Blunt.Data.Factories.Factory.build/1                              66     189.897       0.470  <--
    Blunt.Data.Factories.Factory.build_final_message/1              66     127.517       0.134     
    Blunt.Data.Factories.Factory.evaluate_values/1                  66      25.472       0.264     
    Blunt.Data.Factories.Factory.init_builder/1                     66      23.806       0.266     
    Blunt.Data.Factories.Factory.normalize/1                        66       8.454       0.943     
    Blunt.Data.Factories.Factory.debug/2                           132       4.178       0.529  

  Blunt.Data.Factories.Value.Blunt.Data.Factories.Values.Pro       192      21.930       0.756  <--
    Blunt.Data.Factories.Factory.log_value/5                       175       9.170       0.703     
    Faker.Company.name/0                                            13       3.678       0.065