v2.1.6

This release fixes a bug in determining specificity values during guidescan enumerate. The incorrect specificity values would have shown up if --alt-pam flag was specified with guidescan enumerate. The code was initially looking at the PAM obtained from the kmer file, but now we look at the actual 3-nucleotide sequence at the end of the match. Of course, the specificity values are understood to make sense only in case of cas9.