Procreator will mutate with given probability

I've implemented #46, but the solution requires to pass the value via Procreator's and Godfather's constructor. It is rather bad design.
 
In my opinion this issue can be closed without merging this code. Users of the library can provide conditional mutation via different implementations of the mutate function. It's far better to implement mutate function as it's implemented in BackpackOperators. 

  def mutate(genome: Genome): Genome = {
    if (Random.nextDouble() < 0.05d) { // mutate genome } else genome
  }

It's up to you whether you merge this or just abandon this PR.