Add matrix tests

[Inomares]

This PR aims to improve test coverage of modules in #258, primarily the matrix submodule.

Below follows coverage for each module on the matrix algorithms before/after:

Classes	branches	coverage before	missing after	coverage after
bomb_enemy.py	20	85%	0	100%
cholesky_matrix_decomposition.py	16	100%	0	100%
copy_transform.py	20	81%	11	81%
count_paths.py	14	0%	3	88%
crout_matrix_decomposition.py	16	94%	1	94%
matrix_exponentiation.py	16	100%	0	100%
matrix_inversion.py	38	98%	1	98%
multiply.py	10	90%	0	100%
rotate_image.py	8	67%	0	100%
search_in_sorted_matrix.py	6	0%	0	100%
sort_matrix_diagonally.py	14	96%	0	100%
sparse_dot_vector.py	22	41%	0	100%
sparse_mul.py	66	0%	1	98%
spiral_traversal.py	18	89%	2	93%
sudoku_validator.py	52	87%	7	87%
sum_sub_squares.py	12	93%	0	100%
Total	348	61%	26	93%