Fixed Example Code

Arduino compiler settings such that floating point version of max() was not selected during compilation. This change fixes that. Also incorporates a few other tweaks.

Support for Teensy 4.x

This releases adds support for Teensy 4.x boards, plus addresses a few compiler warnings.

Update to GFX v1.9.0

Update to leverage new features in Adafruit GFX v1.9.0 library release.

v0.9.0

First public release.