[#5] Build recording doubles with rspec-mock doubles instead of rspec-fire.
[#5] Remove rspec-fire.
[#5] Use VerifiedDouble to mock and stub doubles.

  Fix: MethodSignatureValue#modified_class where the value is recording
  double should be the class represented by the class_name of the recording
  double.

  Update MethodSignaturesReport: sort unverified signatures output.

  Known issue: duplicate method signatures in report.