Add lemmatization to get_raw_words util function

[zachd]

Adds lemmatization as per suggestion in #8 by @DeanSherwin

Results:

ORIG 759/1090 | 69.63% | {1: 81, 2: 84, 3: 80, 4: 71, 5: 70, 6: 63, 7: 64, 8: 56, 9: 49, 10: 43, 11: 45, 12: 52, 13: 0, 14: 0, 15: 1}
NEW  755/1090 | 69.27% | {1: 81, 2: 83, 3: 80, 4: 72, 5: 69, 6: 63, 7: 63, 8: 56, 9: 49, 10: 43, 11: 44, 12: 51, 13: 0, 14: 0, 15: 1}
      -4        -0.36         =     -1      =     +1     -1      =     -1      =      =       =      -1      -1      =      =      =

[zachd]

Results as above. Not sure what to make of them?