Node rotation (LL, RR, LR, RL)

[jenyaftw]

Add methods to node class for rotating the tree. This will eventually be used to make tree self-balanced.

A good resource regarding self-balanced trees:
https://www.youtube.com/watch?v=vRwi_UcZGjU

[mykolachub]

Node rotation is part of AVL Tree which is an extended version of Binary Search Tree. For now, that part is frozen because of algorithms complexity.