add solution to Exericse 3.4.

Included is the following file:

	higher_order_functions.py

Thank you!
							Lawrence X. Amlord
							  Apr 10th, 2014
							  Xi'an, China
add solution to Exercise 3.5.

Included is the following file:

	grid.py

Thank you!
							Lawrence X. Amlord
							  Apr 10th, 2014
							  Xi'an, China
add code in section 4.1 TurtleWorld.

Included is the following file:

	mypolygon.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add code in section 4.2 Simple repetition.

Included is the following file:

	mypolygon2.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add solution to Problem 1 in section 4.3.

Included are the following 2 files:

	square.py
	square2.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add solution to Problem 2 in section 4.3.

Included is the following file:

	square3.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add solution to Problem 3 in section 4.3.

Included is the following file:

	polygon.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add solution to Problem 4 in section 4.3.

Included is the following file:

	circle.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China
add solution to Problem 5 in section 4.3.

Included is the following file:

	arc.py

Thank you!
							Lawrence X. Amlord
							  Apr 12th, 2014
							  Xi'an, China