Immunogenicity ligandome

Instead of trying to model the space of immunogenic epitope strings directly, instead let's model immunogenicity by only keeping track of which patterns *can't* be recognized by T-cells. These are epitopes which overlap with the set of "self" peptides used for negative selection in the thymus. 
Seems a little odd that you have a data_path to override this but pass it in nowhere in cancer_pipeline?