fix bug : black height doesn't include the root
	modified:   ch13/red_black_tree_with_bh.hpp
update
 On branch ch13
	modified:   ch13/main.cpp
	modified:   ch13/red_black_tree_with_bh.hpp
	modified:   ch13/redblacktree.hpp
update
 On branch ch13
	modified:   ch13/red_black_tree_with_bh.hpp
refactoring : using Base::members
 On branch ch13
	modified:   ch13/red_black_tree_with_bh.hpp