AWOL:
Sorry - missed the point that you were using a Mega.
Maybe lose the comment?
I've removed the confusing comment that was in the coding; it's strange how some other libraries (Adafruit, Matt Joyce's old library that compiles in pre-1.0 Arduino IDE) work seemingly without problem.
The only difference that I can discern is that the other libraries use Wire.h whereas Karlsen decides to forgo using Wire.h.