Error using recordclass module in Array.py

[JMCanning78]

The Array.py source code imports the recordclass module. When I used
pip3 install recordclass
to install the Python 3 version, I got recordclass-0.12.0.1
When I run the visualization, however, I get this traceback:

Traceback (most recent call last):
  File "Array.py", line 25, in <module>
    class Array(object):
  File "Array.py", line 27, in Array
    Element.__new__.__defaults__ = (None,) * len(Element._fields)
AttributeError: type object 'Element' has no attribute '_fields'

This code is trying to set the default values for the record fields when a new class instance is built. The Python 3 version uses a different name for the "fields" attribute. Rewriting the line as:

Element.__new__.__defaults__ = (None,) * len(Element.__fields__)

works. I'm not sure if that's backwards compatible with Python 2.*.

[JMCanning78]

See pull request #15 for fixes.