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
Is it good practice to place asserts inside conditionals, given that they can be stripped away (e.g. by -O, regardless of its utility)? Maybe assert valueLessThan(...) and place the conditional inside?