Add command-line arguments, mod TEST macro.

Add:
	src/engine.c
		-add argumentHandler(), to handle command-line arguments; the engine
		currently supports only two, so the function has only rudimentary
		parsing functionality. Will be modified with scalability in mind if
		necessary.

	src/unit_tests.c
		-remove statement from TEST() macro that caused the engine to exit on
		failure of a certain unit-test -- if one does, it may be helpful to see
		whether any others fail to identify a potential root cause.