transition back to full viterbi
A lot of changes:
 * Viterbi calls have been parallelized
 * Nasty bugs corrected
 * New SCALE_FACTOR and INSERTION_PENALTY (-p and -s in HVite), -> CHECK
using multiprocessing.cpu_count() + tested output
default insertion penalty and grammar scale factor
correct an options related bug in mfcc_and_gammtones
added insertion penalty and grammar scale factor in the transitions matrix