Bigram clustering

Custom implementation of Algorithms for bigram and trigram word clustering [1] by Martin et al.

TODO: add documentation

make
./bigram -i input.bin -o output.bin -w 10000 -c 128 -e 100

References

1. Sven Martin, Jörg Liermann, and Hermann Ney. 1998. Algorithms for bigram and trigram word clustering. Speech Commun. 24, 1 (April 1998), 19-37.