In this exercise you will implement, in Ruby, several Tree methods.

• add(value) - This method adds a value to the Binary Search Tree
• find(value) - This method returns true if the given value is in the tree and false otherwise.
• inorder - This method returns an array of all the elements in the tree, in order.
• postorder - This method returns an array of all the elements in a postorder fashion (left, right , root).
• preorder - This method returns an array of all the elements in a preorder fashion (root, left, right).
• height - This method returns the height of the binary search tree.

• delete(value) - This method removes a node from the tree. Also add tests for the method.
• bfs - This method returns an array with the tree elements in a level-by-level order (see Breadth-First traversal)