Alphashapes and Python bindings
  * converted alphashapes2d to the new format
  * added Python bindings for alphashapes
  * added sample alphashapes.py that dynamically distinguishes between 2D and 3D
#include <boost/python.hpp>
#include <boost/python/iterator.hpp>
namespace bp = boost::python;
#include "chain.h"
namespace dp = dionysus::python;
void export_chain()
{
    bp::class_<dp::VChain>("Chain")
        .def("__iter__",    bp::iterator<dp::VChain>())
        .def("__len__",     &dp::VChain::size)
    ;
}