Update zfin.py
Update zfin.py

Fixed old filename for ZFIN JSON data.
nathandunn/agr,alliance-genome/agr,nathandunn/agr,alliance-genome/agr,alliance-genome/agr_prototype,nathandunn/agr,alliance-genome/agr_prototype,alliance-genome/agr,nathandunn/agr,alliance-genome/agr