Added dtr option description
Added dtr option description

As said in #19
xseignard/cordovarduino,xseignard/cordovarduino,elafargue/cordovarduino,i-mars/cordovarduino,i-mars/cordovarduino,i-mars/cordovarduino,elafargue/cordovarduino,elafargue/cordovarduino,xseignard/cordovarduino