calculate_SNB.py v0.2

• Input files can now be relative abundance tables. Note that if a relative abundance table is supplied, the --c2 / --pairwise_comparission_cutoff cannot be set to absolute read counts, as was done in the paper (with 5 reads).
• Both --c1 / --presence_cutoff and --c2 / --pairwise_comparisson_cutoff can now be set to 0 to consider all taxonomic lineages with a non-zero abundance.