add pom.xml
add .gitignore
add List interface
add ArrayList and ArrayListTest
add LinkedList and change ArrayListTest to ListTest

ArrayListTest has been renamed to ListTest and modified to allow testing
multiple implementations of the List interface.
add DoublyLinkedList and update ListTest
add Tree interfaces
add NonBalancingBinarySearchTree and tests
add RedBlackTree
update BinarySearchTreeTest to test RedBlackTree
update BinarySearchTreeTest

remove unecessary code
Rename LinkedList to SinglyLinkedList
update README.md