Implement Tree data structures.

[happy-san]

Goals:

• [X] Binary Search Tree.

• [x] AVL Tree.

• [X] Red-Black Tree.

• [ ] B Tree.

• [ ] B+ Tree.

• [x] Threaded Binary Tree.

• [x] Trie.

• [ ] Radix Tree.

[happy-san]

@code-shoily Shouldn't heap be moved into tree directory?

[code-shoily]

Thank you for handling all those Tree implementations @happy-san