Get weblogo data for an alignment object.

    Returns a list of tuples: (posn, letter_counts, entropy, weight)

def aln2logodata(aln):
    """Get weblogo data for an alignment object.

    Returns a list of tuples: (posn, letter_counts, entropy, weight)
    """
    handle = StringIO(aln.format('fasta'))
    logodata = read_logodata(handle)
    handle.close()
    return logodata