Remove a setup.py classifier

Change Node.value to Node.val and minor refactors

Update README.rst and documentation

Overhaul for 4.0

Add MANIFEST.in file

Overhaul for 3.0

Fix a bug in binary search tree check

Add new utility functions using level-order IDs and improve the API

Refactor _build_str function and improve documentation

Improve docstrings and add features to Node class