modified:   chapter2.md
	new file:   chapter3.md
	new file:   code/2.1 InsertionSort.py
	new file:   code/2.3 MergeSort.py
	new file:   code/exercises/2.2-2 SelectionSort.py
	new file:   code/exercises/2.3-4.py
	new file:   code/exercises/2.3-5 BinarySearch.py
	new file:   code/exercises/2.3-6 TwoSum.py
	deleted:    codes/2.1 InsertionSort.py
	deleted:    codes/2.2-2 SelectionSort.py