1.5.6

This is a hotfix release. It fixes the following issues:

• The pvacbind run command would previously error out if one of the input sequences would contain a X stop codon. This update will remove the X amino acid and the downstream sequence before further processing the remaining protein sequence.
• A bug in the pvacfuse top_score_filter code would previsouly result in an error when trying to run this command. This has now been fixed.