New library : I2C 18 bits of resolution A/D converter

#Pinguino can now drive the Microchip MCP342x family. A two channel low-noise, high accuracy delta-sigma A/D converter with differential inputs and up to 18 bits of resolution. The on-board precision 2.048V reference voltage enables an input range of ±2.048V differentially. The device uses a two-wire I2C™ compatible serial interface and operates from a single power supply ranging from 2.7V to 5.5V. The MCP342x devices perform conversions at rates of 3.75, 15, 60 or 240 samples per second depending on user controllable configuration bit settings using the two-wire I2C Compatible compatible serial interface.