Implemented ImageZigzagPersistence * Changed ZigzagPersistence to support a visitor, and implemented ImageZigzagPersistence * examples/rips/rips-zigzag now computes using ImageZigzagPersistence * PersistenceDiagram no longer records zero persistence pairs * Added utilities/memory.h with report_memory() function

#include "grid2D.h"
#include <iostream>

int main()
{
	Grid2D grid(40,60);
	int i = 0;
	for (int x = 0; x < 40; ++x)
		for (int y = 0; y < 60; ++y)
		{
			grid(x,y) = i++;
		}

	std::cout << grid(20,30) << std::endl;
	std::cout << grid << std::endl;
}