Merge pull request #3226 from yarda/fix-use-arduino-protocol-for-programming

Use arduino programming protocol by default for sanguino

ArduinoAddons/Arduino_1.6.x/hardware/marlin/avr/boards.txt

 sanguino.name=Sanguino
 
 sanguino.upload.tool=arduino:avrdude
-sanguino.upload.protocol=stk500
+sanguino.upload.protocol=arduino
 sanguino.upload.maximum_size=131072
 sanguino.upload.speed=57600