ssteval.py: also report totals for nouns and verbs
Profiling revealed a MAJOR bottleneck in c_viterbi() calls to
legalTagBigram() with strings and pure-Python memoization. Caching the
results in o1FeatWeights eliminates ~2/3 of decoding time! (This can
probably be further improved by refactoring the code so the cache of
valid/invalid transitions is maintained across weight updates.)