Converts a list of string ranges to a list of [low, high] tuples.

def _parse_ranges(ranges):
    """ Converts a list of string ranges to a list of [low, high] tuples. """
    for txt in ranges:
        if '-' in txt:
            low, high = txt.split('-')
        else:
            low, high = txt, txt
        yield int(low), int(high)