add 256colors2.py example

I think a runnable example would be nice to have. This `256colors2.py` is a clone of [`256colors2.pl`][perl], which was written by Todd Larason, the page isn't accessible at this moment and may be for some time already. That prompted me to create this example code by mimicking the output, even you can still search for copies online, this serves a simple and complete example using ansicol library.

[perl]: http://www.frexx.de/xterm-256-notes/