rename the folder name
	renamed:    ch2/2.1/Ex2.1_2.cpp -> ch02/2.1/Ex2.1_2.cpp
	renamed:    ch2/2.1/Ex2.1_4.cpp -> ch02/2.1/Ex2.1_4.cpp
	renamed:    ch2/2.3/2.3-7.cpp -> ch02/2.3/2.3-7.cpp
	renamed:    ch2/2.3/ex2.3-2.cpp -> ch02/2.3/ex2.3-2.cpp
	renamed:    ch2/2.3/ex2.3-4.cpp -> ch02/2.3/ex2.3-4.cpp
	renamed:    ch2/2.3/ex2.3-5.cpp -> ch02/2.3/ex2.3-5.cpp
	renamed:    ch2/insertionSort.cpp -> ch02/insertionSort.cpp
	renamed:    ch2/merge_sort_CLRS_style.cpp -> ch02/merge_sort_CLRS_style.cpp
	renamed:    ch2/merge_sort_STL_style.cpp -> ch02/merge_sort_STL_style.cpp
	renamed:    ch2/prob2-1/main.cpp -> ch02/prob2-1/main.cpp
	renamed:    ch2/prob2-1/sorts.h -> ch02/prob2-1/sorts.h
	renamed:    ch2/prob2-2.cpp -> ch02/prob2-2.cpp
	renamed:    ch2/prob_2-3_HornerRule.cpp -> ch02/prob_2-3_HornerRule.cpp
	renamed:    ch2/seletion_sort_ex22_2.cpp -> ch02/seletion_sort_ex22_2.cpp
	renamed:    ch2/sorts.h -> ch02/sorts.h