[NB] Remove site_scons, use `arduino_scons`

 - Remove `site_scons`.
 - Use [`arduino_scons`][1] instead.
 - Add `write_uint8(address, array)` function, to write byte string to
   specified address on device.

[1]: https://github.com/wheeler-microfluidics/arduino-scons/tree/master/arduino_scons