made FitnessValuePair more Groovy (removed get methods and
constructor, made immutable).
ParentChildEvolution updated to reflect these changes.
We removed the last arraylist and made the last for loop a groovy
closure method. also fixed a spelling error. Yay us.
Changed name of ParentChildEvolution to MuCommaLambdaEvolution 
because it better represents the algorithm we are using.