Adds instruction for specifying AVRDUDE_PORT (Makefile)
Adds new 'c' commands to firmware (main.c)
Documents new 'c' commands in README.md
Adds support for new 'c' command in ads7825.py, improves documentation and
adds nchannels kwarg to read_scan()
Adds a fix for an edge case where when the first 255 triggers are discarded
when timer_init() is called with n=1. This also fixes a slight trigger offset
issue in general (main.c)
Adds trigger feedback via LED13 on Arduino Mega board
Adds new scan.py to expose scan functionality on the command line