print queue lengths to usb serial
can_head and can_tail changed from uint8_t to uint16_t
all queue heads and tails are now uint16_t
added usb receive function
corrected clock and tightened tolerance. Added SPI.
Merge branch 'master' of https://github.com/ucdfr/Node-Beaver into develop

SPI
xx
added radio_manager. and removed my vim mks