openag modified Adafruit TSL2561 light sensor driver code.
@file Adafruit_TSL2561.cpp
@author K.Townsend (Adafruit Industries)
@license BSD (see license.txt)
Driver for the TSL2561 digital luminosity (light) sensors.
Pick one up at http://www.adafruit.com/products/439
Adafruit invests time and resources providing this open source code,
please support Adafruit and open-source hardware by purchasing
products from Adafruit!
@section HISTORY
v2.0 - Rewrote driver for Adafruit_Sensor and Auto-Gain support, and
added lux clipping check (returns 0 lux on sensor saturation)
v1.0 - First release (previously TSL2561)
This version has code to integrate into the Open Agriculture Initiative,
Farming for the Future, http://openag.media.mit.edu/
V1.0 - November 2016 - Readout of light intensity in Lux.