Convert a file name into the file plus required indexes.

def file_plus_index(fname):
    """Convert a file name into the file plus required indexes.
    """
    exts = {".vcf": ".idx", ".bam": ".bai", ".vcf.gz": ".tbi", ".bed.gz": ".tbi",
            ".fq.gz": ".gbi"}
    ext = splitext_plus(fname)[-1]
    if ext in exts:
        return [fname, fname + exts[ext]]
    else:
        return [fname]