Mostly small changes to get SIO2Arduino working on a Teensy 2.0 with
the Teensy SD Adapter. The only thing really missing on the Teensy was
the serialEvent callback so I had to put a check for available data in
the loop() function to make it run the callback. I also change the pin
assignments to work on the Teensy.
Merge pull request #1 from FozzTexx/master

Changes for Teensy 2.0