Improve OptimizedSolver's table

[sugyan]

before: #1

after:

test bench_3x20_optimized           ... bench:     210,895 ns/iter (+/- 21,032)
test bench_3x20_optimized_unique    ... bench:     203,921 ns/iter (+/- 2,122)
test bench_4x15_optimized           ... bench:   6,890,625 ns/iter (+/- 756,597)
test bench_4x15_optimized_unique    ... bench:   5,971,875 ns/iter (+/- 782,024)
test bench_5x12_optimized           ... bench:  32,335,500 ns/iter (+/- 3,128,405)
test bench_5x12_optimized_unique    ... bench:  27,448,754 ns/iter (+/- 2,216,140)
test bench_6x10_optimized           ... bench:  76,582,500 ns/iter (+/- 2,331,064)
test bench_6x10_optimized_unique    ... bench:  66,488,420 ns/iter (+/- 1,716,280)
test bench_8x8_2x2_optimized        ... bench:  14,121,679 ns/iter (+/- 560,166)
test bench_8x8_2x2_optimized_unique ... bench:  13,538,100 ns/iter (+/- 128,692)