First feature and test for Suscirptor
Dummy's Usuario should implement the nombre_apellidos method
Created the non persistable model SuscriptorAnonimo to collect the data of anonymous suscriptors
We love FactoryGirl
Added suscriptor trait
Added usuario and suscriptor_anonimo factories
Defining the Suscripcion.suscribir method
Defining the Suscriptor suscribeme_a! method