Temperature/Humidity sensor support

[hpmax]

I added code that will auto-detect and read temperature/humidity sensors including the DS18B20 (through the 1-Wire interface), AM2321, HTU21D, SI7021, and BME280 (all through the external I2C interface). I have a DS18B20 that I can test, but not the other ones. Would anyone like to help me test the code?

[hpmax]

I've released the code to hpmax/sensord, it now supports the DS18B20, AM2321 (which I don't recommend), HTU21D, HTU31D, SI7006, SI7013, SI7020, SI7021, SHT40, SHT41, SHT45, SHT85, and possibly the SHT71 and SHT75 (I haven't really done much looking into the SHT71/75, but the interface looks the same as the SHT40/41/45). The only sensors it's been tested with are the DS18B20, AM2321, and HTU21D. The AM2321 didn't seem to work well. If you are looking for a sensor, I'd try to get the DS18B20 (if you care about temp only), or if you want humidity too: HTU21DF, HTU31D, SI7021, SHT85, or SHT40 (if you can get the SHT41 and SHT45 they will be better than the SHT40, but they don't exist yet). If you do try to use one of the sensors I haven't tested and it doesn't work, please let me know and I'll try to get it fixed for you.