Merge pull request #22 from adafruit/stemma_i2c

Added commented out board.STEMMA_I2C with explanation

Author: evaherrada

examples/htu21d_simpletest.py

@@ -7,6 +7,7 @@
 
 # Create sensor object, communicating over the board's default I2C bus
 i2c = board.I2C()  # uses board.SCL and board.SDA
+# i2c = board.STEMMA_I2C()  # For using the built-in STEMMA QT connector on a microcontroller
 sensor = HTU21D(i2c)