Library update + two more examples

This updates the library with the following bugfixes and enhancements:
1) `chr(255)` command byte in `show()` now padded with zeroes, because stock firmware expects a triplet. Fixes #1.
2) Diagnostic output from firmware is now flushed after each show(), solving a problem on Linux.
3) Added optional buffered mode (on by default) that queues the entire animation frame.
4) Added position tracking to prevent pixel data overflow.
5) More robust RGB value clamping.
6) Adds an explicit `close()` method.
7) Last but not least, documents it according to PEP 257 docstrings convention.

Also, adds two more examples:
1) scanline.py - simple looping 60-frame animation
2) binary_clock.py - epoch/HH/MM/SS binary clock