update URLs for pizza.py homepage

3d OpenGL visualization and one that creates SVG images of dump file

snapshots.

.. _pizza: http://www.sandia.gov/~sjplimp/pizza.html

.. _pizza: https://pizza.sandia.gov

.. _ensight: http://www.ensight.com

  plotting, and visualization for LAMMPS simulations.  Pizza.py is

  written in `Python <python_>`_ and is available for download from `the Pizza.py WWW site <pizza_>`_.

.. _pizza: http://www.sandia.gov/~sjplimp/pizza.html

.. _pizza: https://pizza.sandia.gov

.. _python: http://www.python.org

  it easier to analyze and plot.  See the :doc:`Tools <Tools>` doc page

  for more discussion of the various tools.

* **Pizza.py:** Our group has also written a separate toolkit called

  `Pizza.py <http://pizza.sandia.gov>`_ which can do certain kinds of

  `Pizza.py <https://pizza.sandia.gov>`_ which can do certain kinds of

  setup, analysis, plotting, and visualization (via OpenGL) for LAMMPS

  simulations.  It thus provides some functionality for several of the

  above bullets.  Pizza.py is written in `Python <http://www.python.org>`_

Note that for GL, you need to be able to run the Pizza.py GL tool,

which is included in the pizza sub-directory.  See the `Pizza.py doc pages <pizza_>`_ for more info:

.. _pizza: http://www.sandia.gov/~sjplimp/pizza.html

.. _pizza: https://pizza.sandia.gov

Note that for AtomEye, you need version 3, and there is a line in the

scripts that specifies the path and name of the executable.  See the

visualization for LAMMPS simulations.

.. _lws: http://lammps.sandia.gov

.. _pizza: http://pizza.sandia.gov

.. _pizza: https://pizza.sandia.gov

.. _python: http://www.python.org

Additional tools included in the LAMMPS distribution are described on