Update README.md

-Update Tutorial Link to V12

Author: bboyho

README.md

@@ -20,7 +20,7 @@ Documentation
 * **[Installing an Arduino Library Guide](https://learn.sparkfun.com/tutorials/installing-an-arduino-library)** - Basic information on how to install an Arduino library.
 * **[MPL3115A2 Library](https://github.com/sparkfun/SparkFun_MPL3115A2_Breakout_Arduino_Library)** - MPL3115A2 library required for Weather Shield examples. 
 * **[Si7021 Library](https://github.com/sparkfun/SparkFun_Si701_Breakout_Arduino_Library)** - Si7021 humidity sensor library required for Weather Shield examples. 
-* **[Hookup Guide](https://learn.sparkfun.com/tutorials/weather-shield-hookup-guide)** - Basic hookup guide for the Weather Shield.
+* **[Hookup Guide](https://learn.sparkfun.com/tutorials/arduino-weather-shield-hookup-guide-v12)** - Basic hookup guide for the Weather Shield.
 * **[SparkFun Fritzing repo](https://github.com/sparkfun/Fritzing_Parts)** - Fritzing diagrams for SparkFun products.
 * **[SparkFun 3D Model repo](https://github.com/sparkfun/3D_Models)** - 3D models of SparkFun products. 
 * _**[HTU21D Library](https://github.com/sparkfun/SparkFun_HTU21D_Breakout_Arduino_Library)** - The HTU21D humidity sensor was used on DEV-12081 and prior versions of the Weather Shield so if you have an older version you may need this library to run the examples._