Added binary search tree file and corresponding tests file. Wrote out skeleton unit tests.
Added docstrings to all test functions.
Implemented tests for insert function.
Implemented tests for contains function.
Implemented tests for size function.
Implemented tests for depth function.
Implemented tests for balance function.
Added skeleton classes to bst.py.
Implemented BSTNode methods.
Implemented place method on BSTNode and used it to implement insert and contains methods of BST.
Finished implementing BST.
All tests passing.