added documentation on Arduino Zero compatibility

Adafruit_BNO055.h

@@ -279,8 +279,12 @@ class Adafruit_BNO055 : public Adafruit_Sensor
       VECTOR_GRAVITY       = BNO055_GRAVITY_DATA_X_LSB_ADDR
     } adafruit_vector_type_t;
 
+#ifdef ARDUINO_SAMD_ZERO
+#error "On an arduino Zero, BNO055's ADR pin must be high. Fix that, then delete this line."
+    Adafruit_BNO055 ( int32_t sensorID = -1, uint8_t address = BNO055_ADDRESS_B );
+#else
     Adafruit_BNO055 ( int32_t sensorID = -1, uint8_t address = BNO055_ADDRESS_A );
-
+#endif
     bool  begin               ( adafruit_bno055_opmode_t mode = OPERATION_MODE_NDOF );
     void  setMode             ( adafruit_bno055_opmode_t mode );
     void  getRevInfo          ( adafruit_bno055_rev_info_t* );

README.md

@@ -3,6 +3,8 @@
 This driver is for the Adafruit BNO055 Breakout (http://www.adafruit.com/products/2472),
 and is based on Adafruit's Unified Sensor Library (Adafruit_Sensor).
 
+To work with the Arduino Zero, the BNO055's ADR pin must be high, and an "#error" must be removed from the .h file.
+
 ## What is the Adafruit Unified Sensor Library? ##
 
 The Adafruit Unified Sensor Library ([Adafruit_Sensor](https://github.com/adafruit/Adafruit_Sensor)) provides a common interface and data type for any supported sensor.  It defines some basic information about the sensor (sensor limits, etc.), and returns standard SI units of a specific type and scale for each supported sensor type.