Adding External temp code for TMP36

This is what I've come up with so far to measure the external temperature.  I'm using a TMP36 from Adafruit.  
![tempcircuit](https://cloud.githubusercontent.com/assets/7529831/3061367/bcc47ff0-e205-11e3-91cf-a622617bbb1d.png)   
There's a few things I could try from here: compare this sensor to another temp.sensor(DS18B20), improve precision by changing reference voltage, improve stability by applying a filter, apply weather-proofing, log data onto an SD card or a website, explore using it in feedback control...

What I've used so far comes from Adafruit