Added HypermeasureSpecifier to newmusicmakertools.

HypermeasureSpecifier bundles two settings:

    * HypermeasureSpecifier.counts
    * HypermeasureSpecifier.cyclic

Example:

    >>> from experimental import newmusicmakertools
    >>> newmusicmakertools.HypermeasureSpecifier([1, 1, 1, 2])
    HypermeasureSpecifier(counts=(1, 1, 1, 2), cyclic=True)

Composers will use HypermeasureSpecifier to configure MeasurewiseDivisionMaker
objects.