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
#ifndef __PYTHON_SIMPLEX_H__
#define __PYTHON_SIMPLEX_H__
#include <topology/simplex.h>
typedef int Vertex;
typedef double Data;
//typedef Empty<> Data;
typedef Simplex<Vertex, Data> SimplexVD;
#endif