Prepend all traversal function names with trav.

data_structures/binary_tree/src/(binary_tree.(c, h), test.c)
	-Prepend the names of all traversal functions with "trav" (so,
	`BinaryTree_inOrder()` was changed to
	`BinaryTree_travInOrder()`, for consistency with
	`BinaryTree_travBreadth()`).