Add a compass example

[siddacious]

This PR in an older lib had the good idea to add a compass example:
https://github.com/adafruit/Adafruit_Python_LSM303/pull/4/files

We should add similar code to this lib

[FoamyGuy]

I've got an order that includes some of these sensors on the way to me now. Once they arrive I will work on bringing these examples into the new libraries