Refactor of HMM and Corrector — Corrector now just takes an HMM.  This is more agile than trying to keep the interface general.  Variables under testing are now incorporated into the HMM, such as algorithm type, and thresholds for pruning or surprise.
Unit tested surprise index filtering.
More throrough tests for viterbi_three; revealed a bug in calculating path probabilities; fixed.
SConstruct incorporates all the new variables, and does evaluation.
Fixed bug in scons commandline variable reading; made verbose in the HMM scope, not the Viterbo scope.