Added RoundedRatioDivisionMaker to makertools.

Example: makes output divisions with ratios equal to 2:1 of input divisions:

    >>> maker = makertools.RoundedRatioDivisionMaker(
    ...     ratios=[mathtools.Ratio(2, 1)],
    ...     )
    >>> lists = maker([(7, 4), (6, 4)])
    >>> for list_ in lists:
    ...     list_
    [Division(5, 4), Division(2, 4)]
    [Division(4, 4), Division(2, 4)]

Example: makes output divisions with ratios equal alternately to 2:1 and 1:1:1
of input divisions:

    >>> maker = makertools.RoundedRatioDivisionMaker(
    ...     ratios=[mathtools.Ratio(2, 1), mathtools.Ratio(1, 1, 1)],
    ...     )
    >>> lists = maker([(7, 4), (6, 4), (5, 4), (4, 4)])
    >>> for list_ in lists:
    ...     list_
    [Division(5, 4), Division(2, 4)]
    [Division(2, 4), Division(2, 4), Division(2, 4)]
    [Division(3, 4), Division(2, 4)]
    [Division(1, 4), Division(2, 4), Division(1, 4)]

See the API entry for evne more examples.