Added HID+CDC functionality

I've changed the serial code to the teensy usb serial example
(http://www.pjrc.com/teensy/usb_serial.html) and then modified it to add
the HID keyboard functionality. I believe I have configured the usb
descriptors correctly, and it works with linux. Windows needs some .inf
tweaking.
Reverted USB VID/PID
Merge pull request #2 from JamesGlanville/master

HID+CDC (still have to remove calls to the <stdio.h> library and document USB code)