Add Example: Finding_Roots-Iterval_Method in section 1.3.3.

Included are the following 2 files:

	Finding_Roots_of_Equations_by_the_Half-interval_Method.scm
	Test_for_Finding_Roots_of_Equations_by_the_Half-interval_Method.scm

Thank you!
							Lawrence R. Amlord
							   May 11th, 2013
							   Xi'an, China