Bootstrap binary_tree project.

data_structures/binary_tree/
	-Add brief README.
	-Add basic makefile, `src/`, two placeholder source files.
Add header declarations for all necessary funcs.

data_structures/binary_tree/src/binary_tree.h
	-Declare typedef'd tree/node structs.
	-Declare all of the functions to be defined by this binary tree
	library.
Add test.c; define and doc BinaryTree_create().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Define and document `BinaryTree_create()`.
	-Move `main()` to `test.c`.

data_structures/binary_tree/src/test.c
	-Add a module to serve as the main entry point for tests, so
	that the actual tree implementation can be compiled and linked
	into other executables.
Define BinaryTree_ insertLeft() and insertRight().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Define and document `BinaryTree_insertLeft()` and
	`BinaryTree_insertRight()`; not tested.

data_structures/binary_tree/src/binary_tree.c
	-Define and document `static` method `createNode()`.
Define and document BinaryTree_insertRoot().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Define and document `BinaryTree_insertRoot()`.
Define tap unit-tests for several funcs.

data_structures/binary_tree/src/test.c
	-Use `libtap` to write TAP unit-tests for the project.
	-Define `test_create()`, `test_insertRoot()`, and
	`test_insertLeft()`.
Def test_createDataItems(), test_freeDataItems().

data_structures/binary_tree/src/test.c
	-Define and document `test_createDataItems()` and
	`test_freeDataItems()`, which make it easy to create data items
	for testing and cut down on what would have been repeated code.
	-Add documentation comment to `freeData()`.
Define, document, and test BinaryTree_removeNode().

data_structures/binary_tree/src/(binary_tree.(c, h), test.c)
	-Define, document, and test `BinaryTree_removeNode()`.
	-Add second `*` to all leading `/*` comment delimiters where they
	were missing it.
Def BinaryTree_free().

data_structures/binary_tree/src/binary_tree.c
	-Define `BinaryTree_free()`.

data_structures/binary_tree/src/binary_tree.h
	-Document `BinaryTree_free()`, `BinaryTree_Node_t`, and
	`BinaryTree_Tree_t()`.
Def BinaryTree_isLeaf().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Define and document `BinaryTree_isLeaf()`.

data_structures/binary_tree/src/test.c
	-Define `test_isLeaf()`, to test `BinaryTree_isLeaf()`.
Remove the no longer used test_freeDataItems().

data_structures/binary_tree/src/test.c
	-Shortly after implementing `test_freeDataItems()`, it was
	realized that the data items that it deallocates would already
	have been freed by `BinaryTree_free()`. Remove.
Update README with description/use example.

data_structures/binary_tree/README.md
	-Add a thorough description of this project.
	-Add code demonstrating sample usage.
Implement preOrder(), inOrder(), postOrder().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Implement and document `BinaryTree_preOrder()`,
	`BinaryTree_inOrder()`, and `BinaryTree_postOrder()`.
Add unit test for traversals.

data_structures/binary_tree/src/test.c
	-Define `test_traversals()`, to test `BinaryTree_preOrder()`,
	`BinaryTree_inOrder()`, and `BinaryTree_postOrder()`.
Simplify traversal implementations.

data_structures/binary_tree/src/binary_tree.c
	-Simplify some unnecessary control-flow in
	`BinaryTree_preOrder()`, `BinaryTree_inOrder()`, and
	`BinaryTree_postOrder()`.
Define BinaryTree_travBreadth().

data_structures/binary_tree/src/binary_tree.(c, h)
	-Implement a breadth-first traversal.
Rewrite travBreadth() using a queue.

data_structures/binary_tree/src/binary_tree.c
	-Greatly simplify `BinaryTree_travBreadth()` by using a queue to
	manage the pool of node pointers, rather than a manually managed
	array.
Add unit test for BinaryTree_travBreadth().

data_structures/binary_tree/src/test.c
	-Define `test_breadthTraversal()`, which tests
	`BinaryTree_travBreadth()`, implemented in 65c362e/19ca7f2.
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()`).
Debug README code example.

data_structures/binary_tree/README.md
	-Fix bugs/errors in the README code example.