1.21.0
Refactored App.java to remove duplicate code and elegantly demonstrate each implementation of the Iterator interface. Removed the redundant ItemIterator interface. Added insert() method to TreeNode class to allow for more elegant construction of BSTs.
Consistent UML model naming across all examples.
#778 Implemented BSTIterator. Included comprehensive unit and integration tests. Refactored file structure to be friendly to future contributors with iterators of more data structures. Added JUnitPlatform to enable running test suite across all iterator implementations. Added README to /binarysearchtree to document what it does and how it works.
add rest of class diagrams
