add IS_PIN_SPI(p) to Boards.h
add IS_PIN_SPI for Teensy and Wireing boards
Merge pull request #33 from ntruchsess/spi

add IS_PIN_SPI(p) to Boards.h
made begin methods consistent while eliminating duplication
added init method to simplify systemReset function and enable FirmataSerial->flush() to be called