Add more organization.
Make basic structure for 'Introduction to Algorithms' study group.
Fix notes.org format.
Added exercise 1.1.1.
Exercise 1.1.2.
Exercise 1.1.3.
Exercise 1.1.3.
Exercise 1.1.4.
Exercise 1.1.5.
Exercise 1.2.1.
Exercise 1.2.2.
Exercise 1.2.3
Problem 1.1