Handle various IEDB outputs with incorrect data

[susannasiebert]

As part of investigating IEDB API output anomalies, I identified four distinct outputs that don't match the inputs:

• A string of tab and new line character
• Header only
• Predicted peptides do not match the requested list of peptides. Allele and length match.
• Predicted peptides include requested peptides but also include additional predictions for other peptides. Allele and length match.

This PR handles all of the above cases and retries the request when these situations are encountered.