function scale(out, a, v) {
  var a0 = a[0],
      a1 = a[1],
      a2 = a[2],
      a3 = a[3],
      a4 = a[4],
      a5 = a[5];
  var v0 = v[0],
      v1 = v[1];
  out[0] = a0 * v0;
  out[1] = a1 * v0;
  out[2] = a2 * v1;
  out[3] = a3 * v1;
  out[4] = a4;
  out[5] = a5;
  return out;
}
Scales the mat2d by the dimensions in the given vec2

@param {mat2d} out the receiving matrix
@param {mat2d} a the matrix to translate
@param {vec2} v the vec2 to scale the matrix by
@returns {mat2d} out