words, 0/1 counts  TP 19 FP 1 FN 2 TN 32  precision 0.950  recall 0.905
tf-idf, 1-2 grams  TP 19 FP 2 FN 2 TN 31  precision 0.905  recall 0.905
tf-idf, char 3-5   TP 20 FP 2 FN 1 TN 31  precision 0.909  recall 0.952
