First commit. (V1.0)
V2.1

- Only PB0 used for selection.
- Strobe when high (20.83 Hz), alternate when pulled low (1.98 Hz).
- Use AVR timer.
Change from 4 to 3 pulses in flashing mode.
Change flashing pulse duration to 8 cycles / 13.89 Hz.
Rename 'blinker' -> 'ledcontroller'
Add redundancy in case PCINT0 is missed.
Add .gitignore.
More useful default target.