libgfx: Matrix Math
Author: Michael Garland

## Matrix Math

### class Mat2

This class implements a 2x2 real-valued matrix. Individual elements are represented with `double` precision floating point numbers. To use the `Mat2` class you must include the header

        #include <gfx/mat2.h>

#### Constructor Methods

The `Mat2` class defines the following set of constructors:

        // Initialize all elements to 0
        Mat2();

        // Initialize row 0 to [a b] and row 1 to [c d]
        Mat2(double a, double b, double c, double d);

        // Initialize rows with given vectors
        Mat2(const Vec2 &r0,const Vec2 &r1);

        // Copy values from A
        Mat2(const Mat2 &A);