using arduino cli interface under raspberry pi 2

apt-get install arduino-core

# apt-get install arduino-mk
# BUG: Instead of above line, copy https://github.com/quchunguang/homemake/blob/master/arduino.mk to `$ARDUINO_ROOT`, the root of arduino projects. And, for example, a project named `led` located in $ARDUINO_ROOT/led/, create Makefile,

```mk
BOARD = uno
include ../arduino.mk

Then run make upload to make and upload to Arduino connected with raspberry pi 2.