To fix the concatenation error

[rraadd88]

When dna_features_viewer (installed from pypi v3.1.1) was imported, using this command: import dna_features_viewer, it produced concatenation errors:

1. TypeError: can only concatenate tuple (not "str") to tuple because tuple called aa1 was being concatenated to a string '*', and
2. TypeError: can only concatenate tuple (not "list") to tuple because tuple called aa3 was being concatenated to a list ['*'].

The suggested modification — where respective tuples and strings are converted to lists before concatenation — should fix these errors.

[veghp]

Thank you for the contribution -- an equivalent solution has been merged that also handles previous Biopython versions.