2nd attempt at fixing #147 - keeps Common.mk

may be preferable to pull request #149

updated version to 1.2.0

removed ARDMK_PATH - tries to autodetect path to ard-reset-arduino

removed ARDMK_FILE - so no need to fix case of arduino.mk/Arduino.mk

removed some trailing whitespace

removed need to workaround arduino-mk subdirectory

fixed git archive syntax in RPM instructions

updated docs to reflect changes