Not clear that most examples need to run under Blinka

[dhalbert]

Many of the examples/ use PIL or otherwise assume they're running under CPython, not CircuitPython.

• I think the README could be revised to make it clear this library might be used under CircuitPython or under Blinka.

• The examples that can't be used under CircuitPython should probably include comments in the code that warn about that.

  A user was confused: https://forums.adafruit.com/viewtopic.php?f=60&t=167277