* Move Mutant::Mutator::Generator in a dedicated file
* Mutant::Mutator::Generator#append only forwards mutated node when it
does not equal original nodes sexpession. This does not catch
equivalent mutations, but mutations that exactly reproduce the same
AST. This way a check for not generating the same asts can be
centralized.
* This is in progress code. The plan is to support all literals before
beginning to cleanup and dedup the mutation generation. Have to
understand the AST and the possible mutations more in depth before
making structural decisions here.
* Adjust metrics
* Add initial integration spec on method matching
* Yard and Heckle coverage is at 100% (heckle cov is disputable)
* Rcov does not really make sense as MRI 1.8 cannot reach all code
paths.
