Find all the paths that the sum of the path is equal to a given number.

/**
 * BinaryTreePathSum.java
 * 
 * Description: You are given a binary tree in which each node contains
a value.
 * Design an algorithm to print all paths which sum to a given value.
The path
 * does not need to start or end at the root or a leaf.
 * 
 * @author John Qiao <qiaoshun8888@gmail.com> Date: Jan 26, 2014
 */