compare_poisson.cpp computes the additive and product poisson score
in the following setup.
file1 contains (wordcounts for) all crm sequences from fly.
file2 contains (word counts for) each window in a sequence to be 
analyzed in bee.

compare_poisson_subset uses a subset of words. 
file3 contains the subset of words to be considered.
The output gives window-index and window-score for all windows.

The product version has an underflow problem. Use additive version.

in bin/,
poisson and poisson_subset are the product version. Has a bug.

use: poisson_additive and poisson_additive_subset.
