adding explanation of how to use the calibration script

Author: FoamyGuy

examples/lis2mdl_compass.py

@@ -10,11 +10,23 @@
 sensor = adafruit_lis2mdl.LIS2MDL(i2c)
 
 # You will need the calibration values from your magnetometer calibration
-# these values are in uT and are in X, Y, Z order (min and max values)
+# these values are in uT and are in X, Y, Z order (min and max values).
+#
+# To get these values run the lis2mdl_calibrate.py script on your device.
+# Twist the device around in 3D space while it calibrates. It will print
+# some calibration values like these:
+# ...
+# Calibrating - X:    -46.62, Y:    -22.33, Z:    -16.94 uT
+# ...
+# Calibration complete:
+# hardiron_calibration = [[-63.5487, 33.0313], [-40.5145, 53.8293], [-43.7153, 55.5101]]
+#
+# You need t copy your own value for hardiron_calibration from the output and paste it
+# into this script here:
 hardiron_calibration = [[-61.4879, 34.4782], [-43.6714, 53.5662], [-40.7337, 52.4554]]
 
 
-# This will take the magnetometer values, adjust them with the calibraitons
+# This will take the magnetometer values, adjust them with the calibrations
 # and return a new array with the XYZ values ranging from -100 to 100
 def normalize(_magvals):
     ret = [0, 0, 0]