Adding 20pin literals as keywords
Adding some more keywords
Switched 20pin to system 1 
Bug fixes in mappingTest, use all 20 pins
Rather than using invalid pins (0,1,13), redefine mappings to blink pin 13 LED
Bug fix: Set maximum brightness consistently.

Previously, some functions used 8 as the maximum brightness, while others used 255. Now uses PWMMMAX (8) consistently. This fixes the drawLed bug, and all test patterns display.
Minor formatting
Added Arduino Mega 2560 compatibility.

Allow output to any of the 70 pins of the ATmega2560. Currently uses 20 pins, but could
be extended for larger led arrays (although frame rate would drop). Backwards compatibility
with the ATmega328P is preserved, although only 17 pins are available on the Uno for
Charlieplexing.
Added debugging patterns: allWhite and cycleLeds
Updated readme to mention mega support