Add to tutorials that roslaunch adds data-tail to args

edit

I started my node via roslaunch and discovered a datatail in the last two arguments, I did not now about (used kinetic). This was misleading because I checked for the min args required and therefore not failed hiding the missing args with the ones below. Could someone add this to the tutorials.

argv[10] = 1
argv[11] = __name:=sensor_binder
argv[12] = __log:=/home/user/.ros/log/063c83b2-5491-11e6-8f9d-8ca9827a5146/sensor_binder-4.log