Build and release a Python wheel

[kevin-brown]

https://pythonwheels.com/

Right now, only the tar.gz file is being distributed on PyPI for urwid-readline, which isn't that much of an issue, but it does add some time to installing the package.

This package should be compatible with the Wheel format, considering it doesn't appear to have any C dependencies and it is compatible with both Python 2 and 3. As a result, you should only need to generate a universal wheel and then everyone (on all systems) will get the ability to install urwid-readline with just the wheel, without having to do any extra work.