add solution to Exercise 4.69.

Included is the following file:

	Exercise_4.69.scm

Thank you!
							Lawrence X. Amlord
							  Jul 26th, 2014
							  Xi'an, China
add solution to Exercise 4.70.

Included are the following 2 files:

	Exercise_4.70.pdf
	Exercise_4.70.tm

Thank you!
							Lawrence X. Amlord
							  Aug 5th, 2014
							  Xi'an, China
Rename directory 'Exercises_in_the_Textbook/' to be 'Exercises/'.