Add declaration and stubs for rotations
Add declaration of node metadata regeneration func

The function declared in this commit will regenerate a node's metadata,
e.g. it's height and the node count.
Add implementation of left-rotation
Add implementation of right-rotation
Add implementation of regeneration function
Merge prequisited of left-rotation
Merge prequisites of right-rotation
Add space to comments in left-rotation
Add space to comments in right-rotation
Add space to comments on regen_metadata
Fix regeneration of height.
Add function for subtree rebalancing
Fixup comment in rebalance_subtree
Fixup assignments in rotate_left
Fixup assignments in rotate_right
Fix assignments rebalance_subtree
Fixup: Reference paper in comment in rebalance_subtree
Add warning to regen_metadata
Fix style issues in rebalance_subtree
Merge pull request #74 from neithernut/add-internal-avl_rotation_functions

Add internal avl rotation functions