Modifying ShiftPWM to work with the MKR1000?

Let me warn you: I'm a massive newbie to Arduino and electronics in general.

I'm trying to control LEDs via a shift register using the awesome ShiftPWM library (the improved Redux version). The problem is that it isn't designed for ARM devices like the MKR1000, so obviously, it doesn't compile.

How would I even start to make it compatible? Is it even possible?