Display rotation/mirroring + new examples

This release contains one new major feature:

• ability to invert displays along X (display-, and segment-wise) and along Y axis.

Please note that the constructor has been changed. An extra parameter (3rd) was added to specify mode and the frame buffer pointer is now the 4th param. For most people - those who didn't provide their own buffers - nothing changes.

And two new examples:

• a faster marquee based on display scrolling (by James),
• another marquee example, this time using Adafruit_GFX library.

Examples & Module reversal

0.2.1

Updated readme

Added optional support for Adafruit_GFX library

Changes:

• added optional support for Adafruit_GFX library (to enable use define USE_ADAFRUIT_GFX),
• added getPixel() method (#13)
• fixed problem with memset missing on ESP32 (added in #ifdef) (#12)
• fixed some warnings about unused variables.

Have fun and let me know if you spot any problems! 👍

Compatible with Arduino AVRs, added some examples

Merge pull request #6 from moette/master

Better examples, better memory handling