FastLED 3.1 preview changes:
* 8-way parallel output on teensy 3, 3.1 (portc,portd), due/digix (porta, portb, portd)
* 12-way parallel output on teensy 3, 3.1 (portc)
* 16-way parallel output on teensy 3, 3.1 (portd & portd paired)
* refresh rate limiting
* interrupt friendly code on teensy 3/3.1
* interrupt friendly code on AVR
* interrupt friendly code on the due
* code re-org for future wider platform support