Merge pull request #18 from adafruit/dhalbert-ustruct

Remove obsolete reference to ustruct

Author: gamblor21

adafruit_htu21d.py

@@ -28,12 +28,9 @@
   https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
 
 """
-try:
-    import struct
-except ImportError:
-    import ustruct as struct
-
+import struct
 import time
+
 from adafruit_bus_device.i2c_device import I2CDevice
 from micropython import const