Add example on trailing return types.
Add C++ Primer exercise 3-24.
Add C++ Primer exercise 3-25.
Add C++ Primer exercise 3-26.
Add C++ Primer exercise 3-28.
Add C++ Primer exercise 3-29.
Add C++ Primer exercise 3-31.
Add C++ Primer exercise 3-32a and 3-32b.
Add C++ Primer exercise 3-33.
Add C++ Primer exercise 3-34.
Add C++ Primer exercise 3-35.
Add C++ Primer Exercise 3-36 part 1.
Add C++ Primer exercise 3-36 part 2.
Add C++ Primer exercise 3-37.
Add C++ Primer exercise 3-38.
Add C++ Primer exercise 3-39.
Add exercise C++ Primer exercise 3-40.
Add C++ Primer exercise 3-41.
Add C++ Primer exercise 3-42.
Add C++ Primer exercise 3-43 -> 3-45.