Add M × N Matrix type and matrix arithmetic support

[chrissimpkins]

I am thinking about how to approach higher-level abstractions of finite vector spaces as collections of Vector.

Motivating case: a Bezier closed contour defined as an ordered list of 2-tuple of x, y coordinates in a Cartesian coordinate system.

This begins to head into more extensive linear algebra support terrain.

[chrissimpkins]

Will extend the library with a new Matrix type and provide support for M-by-N matrix arithmetic. I am coming up with an approach to how this will work with the existing array based, fixed-length Vector type.

[chrissimpkins]

#68