split apart dependencies of vaccine peptide selection

* added unit tests for individual ranking components
* vaccine peptide sorting by four criteria (mutant epitope score, negative wildtype epitope score, number mutated residues, distance of mutation start the edge of vaccine peptide)
* print and write FASTA of vaccine peptides with a little mutation metadata
* print epitopes associated with each mutation
It's just like consensus but switches to NetMHCpan if the allele isn't available, I'll add a comment explaining this.