clear old codes
 On branch refactor/ch04
	deleted:    brute_force_find_max_subarray.h
refactor : find_max_subarray, not tested.
	modified:   max_subarray.hpp
update
	modified:   max_subarray.hpp
done	:	 find_max_subarray
	modified:   ch04/max_subarray.hpp
	modified:   README.md