Refactored three functions in order to reduce Cyclomatic complexity

[akerfel]

Refactored the following three functions in order to reduce Cyclomatic complexity.

• BinarySearchTree.replaceNodeWithNode
• RedBlackTree.BalanceAfterDelete
• BinaryHeapArray.heapDown

All of these functions can be found in the folder src/com/jwetherell/algorithms/data_structures

We have mainly created helper functions for the above mentioned functions, making them shorter and more readable.

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